When your site is down how does it affect you site? What I mean do user come back a few hour later or not? Also what is the longest down time you have had?
For me, my forum has had 8 hours down time in one day!
Some come back, some don't. There was one time all the Byethost servers were down 2 days straight. My server was down about half a day because of a tree that fell on a power line down the road.