First point if it’s done a lot of
miles then maybe it’s due, but I’d expect at least 50k a set, my
company had 100K plug changes, then again it wasn’t Honda, and Honda make excellent engines that are sometimes pushing their capacity output, which exactly covers your second point. Not sure if it’s still relevant but the Japanese market was always taxed on engine size rather than output or emissions which is why there are a lot of smaller capacity high output ICE from/in Japan.