Why exactly was it decided that the best time to do maintenance like this would be while 20+ people were online, rather than waiting until the later hours when only 5-10 people are on? It's rather irritating. Just throwing that out there.
Read this post. Also try to remember that Administrators actually have lives, and may live in different timezones. It can be hard to do maintenance at good times for you.
Oh and 99.5% uptime. That's not much maintenance. Just throwing that out there.