In alt.home.repair, on Mon, 25 Nov 2019 21:55:02 -0500, micky
wrote:

If one gets a new asphalt? shingle roof with 20-year Monsanto? shingles,
how long should it last? 20 years?

Mine is only 13 years old and has a small leak already. I can't see the
back half of the roof from the ground, but the leak is in the middle,
not by the chimney flashing.

I watched them put it on and they did a good job. They used famous name
shingles, though I can't remember if it was Monsanto, 3M maybe.

Should have said Baltimore. Sunny summers but not over 95 for more than
a dozen days a year.

No curling on the shingles I can see.