There are a few different methods to control when and if the ability to book expires.
Day Passes (expire weekly or monthly)
Booking Credits (renew monthly)
Booking Passes (no expiration)
Let's go through them step by step. (For all items, we will be working in section Admin Panel > Setup > Plans)
Go to the section Plans > Time Passes When you are setting up day passes associated with a plan, you have the option to provide a number of free passes that expire either Weekly or Monthly. This will be 1 week or 1 month from the purchase date of the plan.
Go to the section Plans > Bookings
When you are setting up the bookings associated with a plan, you have the option to provide a number of free hours associated with particular resources. These expire/refill to that amount at the conclusion of each monthly billing cycle.
Note that you can also provide different amounts of credits for different resources.
Go to the section Plans > Bookings Alternatively to credits included with the plan purchase price, you can offer your members the option to purchase passes at a discount in this section. These passes do not expire.
When a plan is purchased, it shows the member which items have an expiration and which do not.