Thanks for the feedback about the serial input. Will see if I can integrate that behavior with my code.
I added the rest of my code; it's a lot of lines. So I hope it is not overwhelming.
I originally did a lot of my code with the millis() behavior. But I started running into trouble trying to keep the serial and some other events from impacting my display/temperature readings. Maybe I need to take a fresh look at it again, but I have a lot of things happening at the same time (three PWMs for example).