This roof membrane is 21 years old and in EXCELLENT condition, having been stored indoors for 2/3's of its life.
As for the second shingle roof application....LOL...You're wrong. I'm a retired general contractor (licensed for 42 years). That first layer of roofing shingles provides an added barrier to rain, and it still has oils in it to help prolong the life of the new roofing materials.
I'm happy spending a day every two-three years re-coating what I've done. 6-8 hours of work is great exercise for an old guy...as long as I don't walk off the roof......