To access premium services, you need to activate a monthly or an annual subscription. 

Here are some key differences

Monthly subscriptionsAnnual subscriptions
You'll pay a smaller fee upfront, but you pay every month. In the end you'll pay more for a long-term subscription if it's paid per month.
You'll pay a higher fee upfront, but you'll save money in the long run.
Suitable for short-term usage, for example for a school project or other smaller projects.Suitable for long-term usage and especially useful for businesses that need to collect data throughout the year. 
Active for 30 days after payment.
Active for 365 days after payment.
Must be paid by card.
Can be paid for by card or a invoice* (* Standard and higher).

The billing cycle: 

A monthly subscription will automatically renew every month unless the renewal is cancelled. The annual subscription will automatically renew every year unless cancelled. 

Regardless of when you cancel, you will continue to have access to your premium features and limits for the entire duration of the pre-paid subscription period. In other words, if you subscribe and then choose to cancel your subscription on day 5, you will still have access to the premium features for the remaining 25/360 days.