Thanks guys.
Looks like this same stuff...
Dicor Lap Sealantis being called lap sealant or caulk, depending on the seller, but the label calls it lap sealant. I guess it's the right stuff for the roof?
I like the idea of cleaning the old, and just reapplying where needed a little here and there. I hate to clean all of the old completely off and re-apply entirely, and I hate to spend the money on a complete Eternabond application. I like the idea of the front and rear seam thing for the tape (in future?) and self-leveling everywhere else.
This roof has three skylights, three vents, one antennae, three plumbing vents, one air conditioner and a refrigerator vent so that's a lot of work if just some touch up is perfectly adequate.
I'm still open for more thoughts and input.