Originally Posted by
satprof
What would happen if you were to try to re-use those coupons later, although still within the original validity?
I haven't felt inclined to try since that is clearly against the rules of the ticket and fairly easy for the check-in person to pick up on. Obviously exceptions happen (as Viajero described) but don't bank on it, and if someone decides to throw the book at you it could get nasty/expensive.