It all depends on how hard you ride.

If you are always riding very hard, then you aren't putting much weight on the saddle. In that case saddle choice isn't that important. If you are always riding pretty slow and treating your saddle as a seat, then saddle choice becomes priority #1.

Also certain saddles might be comfy when riding on the hoods and a torture device when riding in the drops (Brooks B-17, anyone?).

I have two road bikes that I have set up to be wonderful rides up to 200 km. I'd change them a lot if I was going to do double century rides or longer. On rides that long I would ride a lot less aggressively and put a higher premium on saddle comfort.