I was always told the more you clean them, the dirtier it gets. I knew a boarder who cleaned her gelding regularly with Excalibur and it was impressive how filthy he got up there. Chicken or egg, not sure — but I do think regular cleaning absent a medical reason does tend to kill off the pH balance and beneficial bacteria up in there.
I’ll admit I’ve cleaned my guy’s sheath once in the seven years I’ve owned him. He’s due for a cleaning but he took it so personally last time, lol! N=1 observation but my guys that are out 24/7 stay much cleaner than when they’re stalled regularly.
I prefer warm water and diluted Ivory — which is also my preference for wiping down tack with a damp rag. None of this “single use” stuff in my barn — I prefer almost everything have a broad application of purposes.