A couple years ago, we rebuilt our 2008 RV to repair water damage. I did a lot of searching to find out what caulk sealants work best. The old guys that do their own repairs recommended Urathane or Tripolymer caulk. Names brands they recommended were: Geocel Tripolymer, Sikaflex Urethane and Vulkem Urethane. We went to Home Depot and in the CEMENT department, found Sika (Sikaflex) Pro Select Construction Sealant polyurethane. It comes in white and capital tan colors. It costs about $8.00 a tube for standard sized caulk gun. I just walked out to check the caulk so I wouldn’t be fibbing and the caulk still looks good. No cracks, no separations. I would definitely recommend wiping everything down on old surface with denatured alcohol before any new application.
As noted above, don’t go to the paint department for the above caulk...it’s in the cement department.
We have a guy who owns his own RV repair business who advises us. On the butyl rubber, he told us he keeps it in the refrigerator to keep it from drying out and he also said we should cover any that would be exposed to sunlight with the caulk to extend it’s life on the RV. That’s what the manufacturers put behind window and door frames as seals.
For what it’s worth...