Can you..

[DTF]

..use BettaRevive for more then seven days?

[Adastra]

Always follow the instructions on your fish medication. Personally, I would not use something like Betta Revive--it's a very general medication marketed toward people that don't know anything about betta diseases and can't figure out what's wrong with their fish. Consequently, the medicine is a jack-of-all-trades, but a master of none, so to speak. It would be much better to diagnose your betta's problem and then use a medication that is for dealing with that problem specifically.