Yes. One-time purchases of Premium packages are available for 1 or 24 months (you can freely choose the number of months).
Two Premium packages valid for 1 and 12 months are available for purchasing subscriptions (on Google Play or the App Store).
You can deactivate any Premium subscription at any time (e.g. you can purchase a one month's subscription and deactivate it on the day of purchase which enables you to purchase one month of Premium access).
Please note that when purchasing Premium access for 12 months, you receive a 10% discount, and when purchasing Premium access for 24 months, you receive a 20% discount.