If a specific groove gets stale, I try to switch it up and experiment. Like reverse the accents, or play the ride on the off beats, or add an open hat, or vary the bass pattern, or add a couple of accent notes on the ride bell, or switch from crossing over to open-handed working the weaker hand, etc. But most of all, I've found playing with as many people as I can and
listening to as much music as I can jumpstarts a stale groove. Especially multi-percussive bands like Santana, Al DiMeola, etc. who have so much going on that it stimulates my brain to break down all the different parts and apply fresh, unique grooves to basic patterns. The opposite of stagnation has got to be
inspiration!
When you think your groove is stale and you have learned a lot of different ones, listen to the everyday sounds around you. Check out a copy machine or a vending machine and think about the groove it is laying down. There is so much out there to learn from.
I'm surprised you didn't say add more cowbell!