The deal I did with my son when we built his AMD 4800+ was that he bought the monitor and video card, while I bought and built the rest. He has to keep it online and crunching 24/7. Boinc is set up to release assets when he's using the computer for other activities. As some games and applications reserve and maintain resources, even when they aren't active, he has to shut them down when he's not using them (mainly games).

BTW, the Thermaltake water pump we bought for overclocking died after about 3-4 weeks and he's back with the origonal air cooled system and the 4800+ is back to the factory processor speed. But he's still getting about 800 credits per day from Predictor@home.

I guess my thought is that if you had family or someone local you could trust to borrow some of your systems and let them crunch for you, that could be a viable option. Especially with the older and higher heat producing systems.