The answer to this basically comes down to math...
A monthly subscription = $12.99/month
Let's say you surf only during the spring and summer months (6 months):
$12.99 * 6 months = $77.94
An annual subscription = $69.99/year
$69.99 * 1 year = $69.99
In this scenario, you would save $7.75 and get 6 extra months of Surfline Premium by signing up for an annual subscription.
Why not get the whole year? Might encourage you to throw on a wetsuit and get in the water during those fall and winter months.
You can start your free trial for a Premium subscription here.