I agree, there is no reason you need to use diaper rash cream every day to prevent a diaper rash--it's to treat a rash--thus you only need a little bit every so often.
To prevent, you could use something like A&D ointment. But again, you shouldn't need to. If he isn't eating something he is sensitive too, he's not wearing disposable diapers he is sensitive to, or you're not washing his clothes or diapers in detergent that he is allergic too, there shouldn't be a rash.
Out of my 3 kids, the only one who has had more than 1x diaper rash is DS#2, who wore the darned Dry Max diapers before I knew about all the trouble. Threw them out, and that was it.
Mama to "The Fantastic Four":
DS 02
DD 06
DS 09
DD 12