Certainly a first seeing a site that goes down for maintenance more times in a week than it doesn't.

There is a scheduled maintenance every Wednesday at 0800 UTC.

But I guess you are probably referring to lobby resets. They are required, when we make ladder changes or update our Anti Cheat. No games will be interrupted however, those who have finished their game or were not playing, will be disconnected from the lobby and have to re-enter the newly spawned lobby.