1) Yes its ok. My longest duration was about 3++ weeks without
even restarting or anything. I had my laptop running for a few
weeks to and it still works perfectly fine.
2) My computer has never reached more then 65 degrees for the CPU.
Of course for gfx card, it has reached about 79 degrees under
stress test. But I still don't shut down my computer.
3) In a way, yes, mdmxiaomayi has already explained it pretty well.
Depends on individual processor too and whether its a desktop or a
laptop.
4) Just leave it on if your parents don't say anything. =)
5) My readings for cpu are like this: 46, 56, 63 (min, avg, high)
using core temp which is more accurate for dual cores. If i use
speed fan readings are varying between 40 to 57 degrees.
For gfx card is 36, 48, 65. Harddisk is more less constant between
33 to 39.