It does not hurt to have the extra fields in case you need them but it is not the most efficient way to go about it.
Ideally you would contemplate all the data and details that you will need to make the site function in the way you desire then create or modify the db schema based on your requirements.
If you are going to offer limited licenses then how you would like to make use of them will determine how the info should be stored. If there is only ever a single licensing option then it would make sense to store that duration as part of the product, if however you could have multiple license expiration for a single product and it depends on what the user has purchases then it would make sense to hold this info in a related table that corresponds to the user.
Let us know if you have any other questions and we will be glad to help you with whatever we can.
