use add-ons or invoices

[benFF]

Ok people, more a question preference I think, but I'd be interested to know what you think.

 

I've setup a new whmcs install to just sell email marketing, with one the packages working on a credits system (ie they buy X credits and can send X messages)

 

So, my question is: would you do the credits as add-ons to the package (so a new order will be made for every top up), or just simply create a single invoice for each top up? (Both methods will be fully automated)

 

I can't decide....