How bad is it not to empty your air compressor after each use?

I don't think it makes any difference whether you let all of the air out or not...just be sure there is a valve or something to take pressure off any attached rubber hose, as leaving pressure on that will burst the hose. Also, there needs to be a way to bleed some air and moisture from the bottom of the tank periodically.

The 10 gallon tank on the air compressor, is what I'm worried about.

Um, just bleed it bi-weekly. (I'm not sure if that means twice a week or every two weeks.)

What is an air compressor?

Put a drain valve that will open to allow water to escape

I have a 60 gallon vertical at our farm shop- it's 20 miles away and maybe gets turned on 3 times a year. It's been there for 10 years now and still runs an impact like a champ.

Bi monthly.

No way I'm bleeding it twice a week.

Bleed it once a week. You aren't saving that much time and it will prolong the life of your compresser.

It's more important in the humid months

I don't empty mine, probably should. I do oil my air line before I use my tools.

Leaving pressure on the tank will eventually corrode the pressure switch. Best to release air pressure and make sure you drain the condensation in the tank.

Water in the tank is definitely not your friend.

Set up and auto drain.

You can put one on a timer. Plug in the timer and let it eat if you are concerned.