You can overdo adding sealant on sealant. After a period of time you have made small dams that retains water. Thats not good.
My '97 32' 5th wheel trailer still has the OEM sealant in most places. I check the sealants in the spring just before first trip...then when the trailers put up for the winter.
I have no idea what sealant brand the factory uses in '97 but whats left is still pliable.
I look for cracked sealant and just fill it with Dicor.
The only places that the OEM sealant started lifting was around the useless ski lite and the front cap/roof joint. I pulled all that would come off and added Dicor to those spots with it in mind not to create a pond.
The unit has never leaked. I've washed the roof twice in all those years. Both times was due to tree sap.