If your using top of the line synthetic oils like Amsoil, Red Line or Royal Purple a year is no problem, in fact some of these oils can go 25k miles between changes when match with their synthetic oil filter. Having said that I use these synthetic oils and still change my oil every 5k miles, I do it myself so it only costs me the oil and filter. If I was using "regular" oil I would change it evey 3k miles.
