When setting up a maintenance period it would be nice to see an option to mail all users connected to the host/group going into maintenance or just the selected users from a list. With this it would be possible to create a maintenance period for e.g. next week and inform the users in 1 go with the description given in the description field.
Extra options would be to mail the users on a scheduled time. E.g. 1h, 2h, 8h or 24h before maintenance period is starting.