I think they should reset no matter what for each tour. Of course I dont bother too much with perk planes or tanks, but I think it would bring out some of the hanger queens making fights just that little bit more interesting.
Setting it so it wipes the slate clean each quarter (3 months) would give the newbies a bit of a chance to earn enough perks for a jet, or tiger now and then, so Id be ok with that too.