What is clan upkeep?
Clan upkeep is simply the activity requirement that Battle.net imposes on clans. Battle.net will automatically disband clans it considers to be inactive. To be considered an active clan and prevent the clan from being deleted for inactivity, the chieftain must log in at least once every 28 days. In addition, at least 10 clan members (including the chieftain) must log in once every 28 days.