the big question is - what exactly are you practicing for that long? And are you working on anything with a teacher?
It's possible to break down your practice time into specific skills: hand technique, stick control, foot technique, foot control, 4-way coordination, independence, tempo variations and speed, groove, styles, dynamics, mobility around the set, rudiments, transcription, playing along with recordings,... there are lots of suggestions in other threads on how to break down a practice session - just look around and they shouldn't be hard to find. And if you're breaking things up in an interesting and varied fashion - it's not hard to find ways to easily burn through 5 hours a day.
Anyway - the point is, I'm not sure if you're taking full advantage of the time that you're spending. If you're feeling like things are going downhill - you might not be diversified enough in your approach. Recording your practice sessions is a good suggestion too - although it seems like you might want to only record 10% of your practice time because you also have to have time to critically listen to what you've recorded and 5 hours a day adds up pretty quick if you're trying to listen to all of it!
It also helps to set goals and have a way to measure your progress (that's where having a teacher can be helpful). Working on specific pieces or songs can give you another thing to work on.
Good luck! You've definitely got the dedication!