According to Bruce :
It is "acceptable" to reroof over old shingles but not recommended. In no
time it will look lumpy. It will also not last as long and may cost you
more on insurance.

When I bought my home, I had asphalt over cedar shingles. Allstate wanted
a 30% additional premium for it. Others wouldn't even insure it at all.

I'm not surprised.

Asphalt over cedar shingles is like carpeting over gravel. It'll look okay
for a little while, and then it'll look awful. If you ever walked on it,
you'd puncture it.

Not to mention making the cedar even drier.

Sounds like California, where they often use the cedar shingles as the
only roof sheathing. You can see through these roofs from the bottom.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.