Some buy a few licences at the beginning of the year, and then a few more of the same product later in the year.  They purchase a year support contract at the same time as making each licence purchase.

I can add the same product multiple times to the same account at different times throughout the year, with the appropriate number of units associated against each.  However, when I try to add more than one contract to each account, it won't let me, as they are overlapping periods.  I only get to see one item in the list of available products, even though the account has purchased it at more than one time throughout the year.  Obviously we want to track the expiry of each support contract (for different numbers of units) rather than have them all expire at the same time.

Does any one have any suggestions on how to do this?

Thanks