[paskster]

1) If you expect a certain refund quota, lets say 20 % within 6 months, then you should already account for it: only account 80 % of the actual revenue and adjust this number after 6 months when you now the actual refund quota. This makes it more complicated but it would be the right thing to do and will help you get a somewhat decent financial plan.

2.) If your growth curve flattens out than this approach obviously does not really give you a good representation of how well you are currently doing.