what is a long time for a Mac to stay up?

I usually restart once a week, but sometimes I forget and my mac will be up for 2 weeks and I don't even realize because it doesn't slow down or anything like windows does when it doesn't get shutdown.

i think the longest without restarting was about 30 days but now i restart about once a week.

months, a year

I never turn it off unless it needs to for system updates

i turn mine off every night

I know it's not Mac OSX, but I've had other BSD-based systems with well over 2 years uptime.