You should grease it every month, keep the water level full in the casing.
Keep the blinkers nice and clean.
Keep the ATF level in check.
Your u-joints should be in good condition and checked every month. Or every week if you abuse your pc alot.
Major reasons for hardware failure are from the points I stated above. Like, water seeps in the casing somehow and you get one or two eggs fried back.
Touching the casing bare feet is another reason for hardware failure. (yes it happens RARELY but not impossible)
Point about the money you spend, do it the right way. Post up a thread, stating your demands from the system and budget (and these two things should go along or else...)
Also, after you're done with buying a new PC, get a good stabilizer and above all, get a GOOD PSU! you won't get fried eggs that way. (do set the PSU to 220v before plugging it in or you'd get a boiled egg that'd cost you around 500 rupees to get repaired)
Your PC being the spectator, stabilizer and UPS would be the beauties at the Italian beach.
Buy a good 200W blower and give a blowjob to your PC every 2 weeks or a month
The last time i cleaned my casing, was about 7 to 8 months ago. (Couldn't find the blower when I made my mind up)
Good luck!