Had a leak in my roof from a roof vent. I went to an RV repair shop and asked about taping all of my roof seams with Eternabond. He said that is not the way to go. He wanted to do a $200.00 air test a...
Do the leak test. If done right, it's money well spent.
After a couple years of battling with a leaky skylight I don't trust EB. Caulk/tape are great IF you know exactly where to put them. That's the neat thing about the air test.
The one thing I found that stopped my skylight leaking was Heng's roof seal. Goes on like thick paint, seals anything. Expensive, but well worth it.