The only downside of Eternabond is that a potential buyer might consider it a "hackjob". This is ironic because Eternabond is a lot better than caulk, but appearances sell.
Were I keeping my TT for the long haul, I'd be paying a few people a couple hundred each, and having a day where all the fixtures (skylights, vents) get replaced/upgraded, the roof primed, the tape laid down and pressed flat with a roller, then the tape's edges caulked. However, since I plan to sell my TT either this year or next, I just make sure all the joints are sealed tightly every 90 days.