Well, they will short you. The exchange companies will fill a tank up to the month of expiration and then put it out to the public. If you got that tank and tried to get it refilled the next month, it would not be filled. I have no problem exchanging an out of date tank as I paid for use of the tank when I first got it. I actually think of that payment as lifetime rental(my life not the tanks) because I can exchange that tank regardless of the date. In fact, I do not know if they recertify the tanks, but I suspect not due to the cost of a new tank in bulk for them.
One thing to remember about using propane is that you can freeze the regulator and the gas will stop. The conditions have to be right for this and it does not always happen, but it has happened to me so I always have a spare.
Also a banjo burner will not use all of the tank. That is another good reason to get a refill vs exchange as you may have as much as a third left.