Yep, like ol soundman98 suggests, for your kind of driving, just follow the manual.
I change the oil in my FRS whenever my wife's Saturn alerts us that it's time for an oil change. We drive our cars about the same number of miles over the same time period.
Oh, hesh up all you folks who think Bubba told me that!
Actually, the oil change interval is just inside my short term memory, so, I'm liable to forget to do it, without a reminder.