Heat heat!
To have a computer on for a few days is not harmfull, may be in the 80's but remember that when we have one computer at home there are companies and schools, production houses, etc. that have their equipment runing for the entire week even 24 hours a day with PCI cards and memory sims in every slot.
What is bad for a computer and any electronic device is to be off for weeks or months, humedity can harm the unit.
When you come from vacation, tur on your computer just for an hour or 2 before use it.
I work with lots of audio equipment, usually when I turn them on after a few months they come with wird sound and noises. I have a Roland sintetizer module that I didn't use in 8 months for more than 2 hours. I turned it on 3 days ago and it was making wird sounds in the back ground, I thought the unit was **** up. After 10 hours it was working as brand new, I'm sure the internal heat remove the humedity from the circuits, 3 more month and may be I would lost it.
So, heat can resolve most of the problems.
Another tip is not having a fan pointing to the unit at all times, you may be introducing humedity and dust, many amateur audio engineers do that, they push air in place of pull the heat out. If you push air in to an aplifier in a club, after one week you are gonna end up with a sample of every single cigarret, dust, and kitchen oil on the unit.