Hello, Sir/Madam.
Thank you for contacting us and using our service.
Actually, have currently changed our policy.
We give you 2 domain for free and they are available for a year. If you want to keep the domains after a year, you should pay for them.
Likewise, donated domains should be paid after a year.
In a word, donation just allow you to have 100 domains. It is nothing to do with domain using period.
You do not need to renew the donation. You only need to renew the domain expiration on each domain.
In addition, you should renew the payment after one year by using Paypal.
When your domain is expired, we will let you know that as below.
I am attaching the image in JPG format.