Kohler toilets do not perform well. They have not modified their internal design to eliminate the very sharp bends, so they tend to clog frequently. As far as "holding up over time, all toilets will need a new flapper or flush valve soon or later. One of the problems with Kohler is they have made numerous design changes on their flush valves and they are often available only for Kohler at a very high price, or sometimes no longer available at all. These are particular areas that Toto has addressed. The designs are such that clogs very rarely occur, and when parts are needed, they are readily available at a reasonable price.