Sealane around roof vents

From my experience, there are two ways to know when to re-caulk the sky lights. One, when you see the first water dripping from them inside the trailer! Two when you are up on the roof inspecting the seals. If they are pulling away/ shrinking, or have dried out and cracked from sun exposure. What ever the case, inspection and preventative repairs are better than waiting for the leak!
The best fix I have found, passed onto me by a very trusted RV service and RV dealer, is to remove any loose lap sealant. Then clean the area with alcohol. Re-apply the lap sealant. DICOR makes a very good lap sealant.
Once the new lap sealant has cured, about 24 hours, apply a coat or two of "Liquid Rubber Roof" over the sealant and any other seams on your roof. I've used this product on our last two trailers and have never had a leak after using it! It's not inexpensive, about $50. a quart, but well worth the money not to have leaks!

Bandaid

I wouldn't trust the tape over an existing installation. Better of just using self leveling lap sealant like the original.