Hm, I've upgrade every 4-5 years and do alright. Granted I probably have more money to spend than others due to not having a life of any sort. OS upgrades are required relatively infrequently - XP tailed off pretty recently and I hope Win7 would run for the same amount of time in terms of developer support for it.
Peace of mind versus a console, well, I dunno I always hear horror stories of consoles getting bricked and such, with a PC it's pretty rare you end up losing every component at once (friend's PSU exploded and torched everything once). Only barrier there is knowing how to swap it out or picking good components (not a guarantee, but some brands have a reputation for good reason)
Hey, we're not a tribe, we're a cult.