I assume you have quite a few users with different expiration dates. So yes, you'll generate a unique subscription key for every user.

You can generate one subscription key for all users -- but then it will expire for all users at the same time.

Does this help? Just let me know if you need more information.

BTW, here are two interesting links:

http://www.lindersoft.com/forums/showthread.php?t=1191
http://www.lindersoft.com/forums/showthread.php?t=2895

Friedrich