Maybe I'm being overly ambitious. I think Snowden said his pubkey took a few days and his is only 7 chars.
Trying this on my laptop but I think I'm going to run it on my Ryzen desktop as well.
Discussion
Ran on a 10 core Mac with an M1 for 5 days. Found 15 6 character npubs and none with >= 7 characters. Found the first 6 character one in 1.3 hours.
Have been running for another 6 days on a 12 core Intel Linux workstation and have not found any >= 7 character npubs yet.
The jump in difficulty from 6 to 7 characters is impressive.