Firstly: already-installed software can be used forever, whether you have access to updates or not.
With each purchase, access to personal support and updates to install/update to new releases of WP-Optimize is for 12 months. (As is the case with about 90% of the premium WordPress plugin market).
After 12 months, your license will be automatically renewed (subscription), granting you access to personal support and updates for other 12 months.
To repeat: if you prefer to cancel your subscription before the end of your billing period, then your installed software is unaffected – it will remain installed and you can carry on using it.
Posted in: Licensing, Subscriptions and Legal Questions