Yeah, our official line is basically "we do our best to provide the best uptime we can".
Web host uptime guarantees in general are pretty much bogus. Who gets to measure the uptime? Is it over a year, a month, a week, a day? What happens if they don't hit the uptime guarantee?
And honestly, if our service has had some problems and somebody wants to leave because of it, we generally won't have a problem giving them a refund even if it's after the original 91 days!