How often can a cat be bathed?

by Pico
(Reno, NV)

My cat is elderly and has started to urinate in his bed while he sleeps. I put a puppy piddle pad down and change it as soon as I see a wet spot under him, but he often does it in the night and sleeps in the wet urine until morning.

Consequently, his coat becomes filthy and he reeks of urine. He won't clean himself when he's that nasty, but he yanks his hair out in clumps.

I've taken to bathing him. A nice gentle shampoo washes his coat clean and he seems to appreciate it. He resumes grooming himself and seems to be more active, more energetic afterward. Until he pees himself a few more nights in a row, then he's filthy and miserable again.

I know cats hate baths but this is the only thing I can think of to help keep him clean. A filthy, urine-soaked cat is a miserable cat. How often do you think is safe and reasonable to bathe him?