I agree with MRC01. Both your oil & filter should be good for a full year. Actually, you oil's probably good for two full years (7 qts! ). With "mostly highway" miles, I'd run it that long without worry, but most here would probably recommend a UOA after a full year. I'm not too familiar with Napa Golds, but aren't they one of the better filters? They're probably good for two years/12k miles too, but I know folks here tend to be a bit squeamish about leaving filters on that long.