That is true, all packages are valid for limited time, this is a nature of all services like that. Service has its cost associated with providing opportunity to use it, even if no one is using it. We are still obliged to keep our servers running, pay salaries to admins, pay for hosting etc.
When package is close to be expired, there are two options: let them expire or buy new package. When you buy new package, expiration date gets prolonged, and old unused pages get prolonged too. If you had 80 pages unused and buy 100 more, you now have 90 days and 180 pages.
If you only need 200 pages evenly distributed over whole year, basically you will need to buy $9,90 package four times a year, and actually will have possibility to recognize 400 pages. Unfortunately, we currently don't have cheaper price points in our price list.