The Food Corridor's billing plans are set-up to be monthly, where unused hours or credits don't roll over month to month. However, here is a workaround that can let you make this happen.
Set up a Standard Fee, Credit, and Plan
Create a Standard Fee (one-time) and call it 'x plan initial fee.' This fee should be in the amount that you want to want to charge over x number of months. For example, if you want to offer 50 hours over 6 months, at $30/hour, make the fee amount $1,500 ($30/hr x 50 hours).
Create a Standard Credit (one-time) in the same amount as your fee and call it 'x plan credit amount.'
Create a Time Based billing plan. Make the plan visibility private, give it a descriptive name such as 'startup credit burn down plan,' set the base hours to 0, set the base rate to $0, and set the overage rate per hour to $30 (in this example).
Or, instead of creating a Time Based billing plan, you can simply keep the client on Hourly. Both options will draw from the credit amount before charging the client. The difference is that when the credit is used up, the hourly plan will start billing the client on the day of their bookings (pay as you cook), vs. the time based plan will bill the client monthly for all their overage hours at one time.
Assign the Fee, Plan, and Credit to your client
Add the Standard Fee 'x plan initial fee' to their account. Clients > Client name > Fees/Credits > Add
This one-time fee should bill within 24 hours or you can charge the fee on the spot.
Either assign the client to the Time Based Billing Plan 'startup credit burn down plan' to start the next month (Clients > Client name > Edit > Billing plan) or keep them on Hourly. See the difference above.
Once the fee has been paid (check the bill on your Billing tab), add the Standard Credit 'x plan credit amount' to their account. Clients > Client name > Fees/Credits > Add
Let the system work for you
The credit will be spent down as the client spends hours in the kitchen, and the credit will roll over month to month.
Once 6 months has gone by - or whatever time period you're working with - the client can be converted to a different plan or put on hourly, or you can start the process over again.
If the client doesn't have any credit left, no action needs to be taken.
If the client does have credit left, add a custom fee for the exact amount of that credit, to cancel it out. Clients > Client name > Fees/Credits > Add