When do you upgrade your PC?

When it stops working. If I know what's wrong and I can fix it with limited expense (like a replacement hard drive), I'll try and push it for a year or two more.

Never, due to erm... A... Limited amount of dispendable funding.
So I basically just replace the parts as they die.

When the pc is near death, hoping my current computer lasts for 5years b4 i build a new one. Not rich enough to be updating every year

only owned one laptop (excluding one that got ran over after just a year) and one desktop in my pc life over the last 7 years

1) when AAA games can't run 60 FPS on low(sometimes very low if the option is there, as long as it doesnt turn into a turd)
2) parts crap out on me
3) upgrading becomes dirt cheap(like a new vid card for next to nothing)

if I have to do alot at once, I try to future proof it for the most part(I regret going to cheap on my current MB, but it would be alot of work to change it now)
atm only things that need upgrading are vid card(cant handle ultra for some of the latest), and MB(atm I cant even use all my case hookups), but nothing necessary for upgrading this holiday

I am considering new monitors(need a pair of 23-24" monitors with DVI plugins that support 1920x1080).. kinda tired of mismatched monitors running 1680x1050 >>

When I have money and when my current PC can't run new AAA games.