M Ecks has your answer folks. ^^^^^^^^^^^^^
There is not yes or no answer on this topic.

We had a slant six on the road for about 40 years. A valve lash check in 2010 confirmed no valve seat recession.

Just like M Ecks, I had a big hydraulic cam pounding on 1967 big block heads. After a few summers of heavy beatings. I noticed 3 mph of trap speed missing and took the engine apart. We found half of the ex seats were sunk down. Fact is the engine ran totally fine and with 12 sec runs. I'm sure most would say making good power but the lack of lead or hardened seats definately deterioated my engine.