Originally Posted by John Clark
Yep, I always keep those. They should work after each upgrade. They may not work when you switch devices, though.
Most are keyed to the PIN. I have found that most developers (assuming you don't abuse the privelege) will have mercy if you've moved to a new device and issue a new code for a new PIN at no charge. I don't know that Handango or another vendor would be so understanding, I usually go directly to the developer.