After each subscription renewal your quota is reset. Then, the total number of tested page views remaining from the previous month in your account will be available for you to use next month.
For example, if you have a 5,000 page views plan and only use 3,000 page views, the remaining 2,000 will remain available to you. So, next month you will have a total 7,000 page views (5,000+2,000) in your account.
However, maximum page views in your account at any given point cannot be more than five times (x5) your current plan. For example, if you have a 5,000 page views plan, your account can never have more than 25,000 cumulative page views.
In case of unsubscribing, the accumulated visits are lost and the available quota of the free plan is restored (500 tested page views).