http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107-7.html

I bought my ATI Radeon HD 5770 in 2010 and looking to upgrade most likely to a  GTX 680.

Well my PC came with a gtx 550 ti a couple months ago and I'll probably upgrade to a gtx 670 or 660 late this year or early next year. After that it'll be a while, a couple years at least especially since I'll be spending all my gaming funds on next gen consoles.

I usually change my graphics card when I change computer. I kept my last PC for about 10 years so by that time I couldn't run any new games.

I change my graphics card...

whenever a game i want to play doesn't run.

All I've got a Radeon HD 4600... and it still plays everything. Not at max graphics... but i'm generally a "turn graphics down for performance" guy anyway.

Graphics cards last a heck of a lot longer with this generation of consoles. Only PC exclusives really push it, which is why Witcher 2 made me buy a new card, first one in about 4-5 years thereabout (8800GTS -> HD6870).

None, because I got my first gaming computer this year, and i think the graphics card is attached to the motherboard.

whenever I have the money to double my GPU power lol

Never since I don't game on the PC.

I change graphics card, each time I change computers. Probably every 5 years.

I change my graphics card whenever it seems worth it. I went from an HD 4670 -> 5750 -> 7850 on one PC and I went from a 7900GTX -> 8800GT -> HD 5870 on the other. I doubt that I will need to upgrade either computer until for a couple more years as I doubt that the next generation will be that powerful. I usually aim to upgrade once every process node so 90nm -> 65nm -> 40nm etc but this console generation has lasted so long...