There's no maximum length for a subscription. A subscription renews automatically every month for an indefinite period.
To stop the automatic renewal, just request a cancellation in your app. Your subscription will then end at the end of your current monthly period.
Note: you can use your parking garage until the last day before your subscription's cancellation takes effect.
You can cancel directly in your Yespark app. Just go to the "Subscription" tab > select the subscription in question > "Cancel Subscription"
You can also do it from your web account ("Subscriptions" tab > find the subscription in question > "Manage" > "Cancel").