I think that better look at the moneyback guarantee options. Some web hosts (webhostgiant.com, OTSH) have 90 DAYS. I believe that proves that they come once and forever and tthey sure that everything will be ok with their uptime.
No I do not think so...you will see many companies offer a 99.9% uptime guarantee. Yes, technology now a days is getting a lot better and hosting companies are getting great uptime ratings...but there are still flaws and some servers experience some downtime; so no, it's not quite to 100%
There are always problems with servers, but it's how the hosting companies prepare for those outages that makes the difference. It's important to have a well trained staff that constantly monitors and maintains the servers. If you're looking for a company that has the best up-time, you'll probably want to check out sites on the web that monitor those - that way there isn't a biased opinion.