How often do you reinstall Linux?

Because I test a lot of software, including software built from source and provided from PPA (for Ubuntu), I reinstall GNU/Linux on one or another of my machines fairly often. Don't worry, this is a painless process because I have the root directory, swap, and home directory on separate partitions.

Example partition setup:
/ - 20GB (this is probably generous)
swap - 4gb (or 2x to 2.5x RAM size)
/home - 225GB (or the rest of the hard drive space)

When I reinstall, I simply set the installer to see the existing /home and swap partitions, then I have it reformat the root "/" directory. Also, since I use the same basic username when reinstalling, most everything that worked in the previous installation, simply works after the install. This is because the user space is perfectly separated from the system space in GNU/Linux.

Plus, installing GNU/Linux is so quick, it's very easy to "refresh" your system whenever you want.

I am a tinkerer and regularly change distros and versions. Sometimes in a virtual machine sometimes not. Right now I'm running Fusion 14 on my older Dell Inspiron but play around with Puppy 5.4 on my Samsung ultra booting from a flash drive.

I do it once a year on my work computer whether I want to or not...Linux basically never requires a re-install - so I set up my own dates to make a thorough walk-thru of my hardware, drivers and codecs just to make sure everything is still upto snuff like I thought it was before I re-installed. Now my lab computers that I try the many flavors of Linux - I do installs and re-installs on those weekly, sometimes daily depending on how badly I screwed the system up with my tweaks and scripts. Sometimes I screw the system up just to test newer installation scripts. You know - you can create your own scripts with BASH that work way better than the batch.files we used to use in MSDOS. Ubuntu and flavors like it have almost made the installs so idiot proof that installing is actually boring...that's why anyone learning Linux or just re-installing it, should download the Ubuntu "Alternate CD" and install from that and teach yourselves Howto Partion, the Re-partition a few times with different size partitions and primary and extended versions, then create LVM installs in them and then encrypt the whole freaking drive on top of that. Internet security starts with the Hard Drive/s. Making them invincible is paramount. Making partitions hidden and secure is 1st and Most Important if you surf the internet or have e-mail servers hitting the internet fully exposed to the wire to serve your e-mail. Remember - make your / 30 gigs and /var 60 gigs and you'll never have to worry about over-installing on them or your e-mail database and storage (mailboxes) getting to big.

As always, responses are constrained by the wording of the question. Mine should be 'Almost never'. It would be 'Never' but for the occasional change in my network's hardware configuration or a new Debian release.

G & S got it about right: 'Never!' 'What, never?' 'Well, hardly ever...'

The only time I would consider reinstalling would be for a major upgrade and at that time the computer is usually obsolete and a fresh installation on new hardware is what I normally do.

Obviously there is a difference of opinion concerning what defines reinstalling of Linux.
My definition is based upon the OS malfunctioning in a way that reinstalling it is the only option available left to get the OS to perform properly. A defective hard drive, in my opinion, requires an initial installation not a reinstall. An upgrade, is little more than a major update, and not a reinstall although some may decide to do an initial install for various reasons rather than just update or upgrade their OS.
To me the point of the question should be in determining how often a malfunctioning OS (Linux) requires reinstalling to eliminate the problem. Quite infrequent, I would imagine.

I update on every new release (of Fedora which is the one I use) i.e. about every 6 months.

But reinstall? May be when the life of my hard drive comes to an end I'll have to.

Do not recollect a reinstall done in at least last 5 years or more.

exactly i often upgrade my linux instead of reinstall when a new release comes out. My linux is Ubuntu.

When I used SUSE 8.0,8.4,9.0,9.1,9.2,9.3,9.4,10.0, I would have to reinstall about once a month, sometimes,more often. Install of 11.0 killed my computer for good. I've tried several others and finally settled for Elive. It is not perfect but I really like it. I love my desktop now! And I really like Debian,now.

We use CentOS and Scientific Linux because of the cost and the
long lifetime. We do a reinstall when the installed version is
declared at "End of Life" by Red Hat.

I have been a distro-hopper, checking out new distros every month via my subscribed magazine (Linux Format) free cd/dvd's. I always end up back at Linuxmint. Recently I added Linux Mint Debian Edition to my Samsung N130 netbook and don't intend to install anything else on this machine as it works perfectly as a rolling release.

In nine years, using less than first rate hardware, have I ever (fingers crossed) had to reinstall any Linux distro on any particular machine. This goes to show the resilience of the hardware as much as the reliability of the OS's. Once the OS bites the disk the thing will run until some, as yet unknown, catastrophic event occurs. On the other hand I have re-installed Windows XP as often as once per year, and spent 20 times more hours on maintenance! The main causes of trouble with hardware have been Power supplies(3), Hard disks(3) and Memory(1). Fortunately the hardware faults did not destroy the integrity of the OS's because I used smart hardware error detection and installed UPS's after the only memory failure (caused by a sudden power cut during a thunder storm).

Once every year or so to switch between Fedora and Ubuntu depending on which one looks nicer at the time.

just:
# apt-get update && apt-get dist-upgrade
is enough to make my Debian box happy.

I use the LTS version of Ubuntu, I perform a full reinstall upon release of the new version, which is every couple of years. It works well for me, though takes a few days to get all those fiddly bits back up and running again, (personal tweaks and installed app, drivers, etc), things that are not out of the box, ie dvd playback (still).

Been running Archlinux on my Dell D610 for about three years, no need to reinstall if its working fine!

I still run Kubuntu 8.04. It works well, I still get updates, does everything I want to do. It was current when I built this machine. Thus my answer of never as I have never reinstalled on this machine.

I use Ubuntu since 5.04 LTS now I am at 10.04 LTS, the only time I have to reinstall is when a new LTS version comes out, or a HDD failure, nothing compare to my old buggies Win32 boxes that I had to reinstall every 2 months or so.

They _did_ say reinstall. Should have differenciated between your "main" machine, or only machine. Some folks have multiple pcs, and may ungrade a 'test' machine whenever they're interested in a new (version) of an distro. I have an old laptop, and I'm too poor to upgrade memory, so I don't do VM. So I wait, try the Live CDs, and upgrade after testing. Usually a couple years or so.

I use gentoo because I can stay up to date at all times (unless a HDD fails). I find it is a lot easier to maintain and to customize as well.