When I woke up my coach from a 4 month hibernation last month my driver side inner dual was about 35 lbs light. Tire tech struggled with finding anything & ultimately found the metal stem had a slight (very slight) leak. Leak was not where it screws into tire but stem was allowing a small amount of air out through the core & air was escaping past the TST cap. Didn't realize that could happen. Regardless he replaced the stem & we're golden. Anyway, new tires will likely run you several grand YES I would let them install new stems for $85. Nothing lasts forever.