You must have less than 6 months of support remaining to be eligible to extend or renew it. The support cost is calculated as a percentage of the item price (the price paid for the item license).
To extend or renew support, please ensure you log into the Themeforest marketplace account used to purchase Avada and follow these instructions.

Do you qualify for Avada Grandfathered Support? You will be eligible if you purchased an Avada license BEFORE September 1, 2015. For more information, please see this help file.