they don't look any different than a normal toilet to replace. with the larger than normal flapper, as it starts to get soft, it can collapse into the hole probably sooner than a smaller one. I saw some toto models that came with something slightly different for the flapper valve - it was more of a plastic frame with a washer on it than being all rubber. Don't know which model it was, but it isn't on either of mine. Also not sure if it is available as a retrofit or if it would last longer.
someone else said that the fill valve on Toto is made by Korky. You might find info about it on that site.