4 months. Got an i7-2600k / GTX 590 / 12GB DDR3-1600 rig late last year to supersede my Core2Duo E8400 / 2x GeForce 9800GT / 4GB DDR2-800 rig (Now runs with an FX 5200 as a file server) which I got in 2008, which had replaced a shitty Dell Dimension 3000 which ran that FX 5200 since 2005. So I'm on an update cycle of about 3.5 years. Probably less in the future, but that doesn't bother me. I like flexible machines that I can easily repair and upgrade myself. Both of my desktop chassis can hold 5 3.5" HDDs.

I also got a cheap HP laptop with an i3 370M / 4GB DDR3-1333 for school around the same time. Both are running Arch Linux and the desktop runs Windows 7 Ultimate for games, a few 3D rendering programs, etc.

Now I just gotta update my monitors, which aren't uniform at the moment : \

Also...

FUCK APPLE. I'll be buying/building desktops forever. I figure this rig will last me about 2 years with no upgrade, then I'll start looking into new parts.

However... I'll probably invest in a good tablet in the future, as a mobile terminal. I like my laptop, but it's 15.6" and if I can get something smaller that has a better screen and good wireless capabilities that I can hack whatever I want to on it, I'll take it :U