When the Premium membership is going to end it will be good to have some kind of alert to the members like its going to end in 1 month or 1 week so renew now. Right now there is no Alert here or via email.
If someone wants to renew, wouldn't they just have one of the normal renewing plans? Also, you can always see the exact day it will expire on the page you sign up for upgrades on... https://forums.digitalpoint.com/account/upgrades