I have a loop that runs really fast at first (15+ records per second),
but then continually slows down (2 per second). It seems to be after
2000-3000 records. It gets much slower when excel is not selected and
speeds up when it is selected. I read some information on optimization
and it helped speed it up at the beginning, but the problem of slowing
down still occurs.

Has anyone heard of this?

By the way, I read records from sheets and write back to them. I also
have a SQL query in a sheet that refreshes for each record.

Any suggestions are welcome.