Renewals before renewal time

I was thinking about renewing for another year even though my subsciption does not expire until May to take advantage of the 30% special (yes, I just saw it but, in all fairness, I was away for two weeks getting married!).  Unfortunately, I do not see anyplace to renew, only to upgrade my plan until my expiration date. 

Could someone just confirm that I can not renew until later and that I am not being my normal obtuse self and missing something? 

Also, just out of curiousity, what is the time period in which we can renew?  This is probably somewhere obvious, but, for the life of me, I could not find it even with a forum search.

Thanks for the help!