I've got a 2000 Yamaha Kodiak 400 and was told the same thing when I bought it new. I took it in for its first scheduled service (which was included when I bought it) and when I asked the service tech what he did, valve adjustment was not mentioned. I think it is more of a warranty thing. I'd do it during the initial warranty period if I were you so if you have a problem, it does not give them an "out" on your warranty. Since then, I have not had mine readjusted and it is running fine for 5+ years now. I'm going to take it in for a checkup this summer though before leave for an extended hunting trip to CO this fall, primarily to get it jetted for high altitude operation.