Each subscription fee (see Fees) is setup for the current season only. The time to prepare new fees is July so that they're ready to go on sale on 1st August, one month before the new season begins (some people like to pay early).
It's not necessary to create new fees from scratch as one season's subscriptions are usually pretty similar to the previous season's, except for start and end dates of course. Instead, simply find each subscription in the list and then:
This will create an identical set of subscriptions for the new season that won't go on sale until the 1st August.