Right now, Membership Pro does not allow for a user to "buy" more then 1 instance of a plan which makes sense in a lot of cases. However, selling webdev, hosting or other related services, I sometimes find myself in a position where I have to make a second account for someone who will purchase two or more websites...
It would be great if there was an option to sell a plan several times to the same account and I believe it would enlarge the scope of Membership Pro to a lot of possibilities.
Something to consider, especially since I've seen this wish passing through earllier...
Meanwhile, I'd like to congratulate you for you great work. I keep using Membership Pro and Edocman with a lot of satisfaction!