I pretty much just replace video cards until my processor cant handle new games. My current desktop is a 6-7 years old Gateway fx-6100. It runs most games on high/ultra, no need to replace it and waste money until shit starts to break. Only upgrades are taking from 3 to 9 gig ram and swapping from a 4850 to a 550ti.
When it dies, I will most likely give up pc gaming. There are very few games I like to play now and some of these new games just look crap.