Are you are talking the cushions you put on the seat of the saddle?
I have a sheep skin one. The leather part sits on the saddle the fuzzy wool part I sit on. It is nice and warm and cushiony. I only use it in the winter though, although I know some people leave them on year round.
I know a trainer lady, who rides all day and she has the foam Tush Cushions that she uses all the time. She actually will wear out a couple of them a year.