As DavidR stated, my scans got progressively longer as more files were added to my PC. The subject line does suggest it happened in step function fashion with the latest Avast update, so my choice of words could have been better.
As of today, I have managed to get my standard scan down to 1 hour, 30 min, so that is a big improvement. This was a result of deleting a lot of files that were not used, cached, etc. I also did some other maintenence, and followed all by defragging.
So I apologize for the misstatement of my subject line, and I would like to thank DavidR for his kind support.