That's usually acceptable. Annoying, no doubt, but those 45 minutes a month don't usually happen in 45-min blocks monthly. It's more like a few seconds every day, and a sparratic issue once or twice a year causing a few minutes.

SLA's commonly agree to 99.9% (and I've dealt with some picky clients), though 99.99% would be better, it's an acceptable amount. Servers break, people need to deal with it when they do, and we aren't all robots.