Usage :: Tier limit set to be reset annually, invoice created monthly

[Rxbsxn]

Hey dear KillBill Team,

In our business, we have a case where we provide year add-ons to our clients with specific free limits e.g:

Small Addon (paid anually)
Have the following usage tiers (the usage is billed monthly):

• 50x Usage Unit free
• After using these 50 units, client will pay 10 EUR for each unit used

The usage has to be billed monthly, so we can generate an invoice for the clients who reported more than the free limit is.

For now, we are doing a workaround by reporting the free limit so (50 units) plus real monthly usage every month:
So:
50 (free limit restarted every month) + 5 (real usage done in the month) = 55 -> This is what we report to the Kill BILL

Is there any chance to have the limit to be restarted every year, but the invoicing done every month?