How often do you buy a new computer?
enough to buy once powerful power supply and the best (by far) processor (course, and the motherboard and all, to ensure the full performance of the processor). Then I change the video card, depending on the issue of new DirectX API. it is if you want to play with better graphics (again, for now). If you just simply sit in social networks, or watch movies. can, in general, do not change until you get bored or do not break at all. for 15 years, I have changed only 1 time a computer, but about 5 video cards (including because of their breakdowns).