I have twelve bikes with seven different saddles, and I'm happy with all of them. There are a few saddles that have worked well for me, so I have them on more than one bike, but I haven't tried every saddle so I'm sure there are lots of others that would work just as well. I have a few saddles that start to get a little uncomfortable after 6-7 hours but are totally fine for shorter rides, so I don't put those on my long distance bikes. I like leather saddles for long distances, but they are a bit more expensive and seem to wear out faster for me than other saddles so I only put those on my long distance bikes, which are ironically not my highest mileage bikes. When saddles wear out i find myself replacing them with something different instead of the same thing. The whole reason I have more than one bike is to try different setups to see what I like, which obviously doesn't work if I put the same equipment on every bike. I would guess that it's pretty unusual for someone with a lot of bikes to have the same saddle on all of them.