Each theme is bound to Envato rules, and depending on your choice when you buy a theme, you get 6 or 12 months of included support from date of purchase.
It means that even if you will not use a theme, your time of support will still be the same. More about it can be read here https://themeforest.net/page/item_support_policy
Cause of that, you can have problems with registering to our support forum, if you support have already expired, and you will have to renew it.
How to renew support
Please follow the instruction provided by Envato here: https://help.market.envato.com/hc/en-us/articles/207886473-Extending-and-Renewing-Item-Support