I really hope this is not the case, and I do not think it is, according to this:

http://www.avast.com/eng/renewals.html

On that page, it says you have 30 days after your license expires to renew at a 30% discount.

Otherwise, what if you purchased the license on Nov 29 or Nov 30? You would get 1 or 0 days to renew? No, it has to be 30 days…