So my subscription expires in 50 days.

There’s a banner on the top of my Avast program telling me that my license expires in 50 days. I’d like to go ahead and re-registers but there doesn’t seem to be an option to do so. Others here on the forum say that you can re-register from 30 days onward. Is this the case? Do I just need to wait another few weeks then to re-register?

You don’t say what avast version you are using ?

The avast user interface (certainly the case in the free version) changes after the 30day notification. In which case the avastUI > Settings > Registration (free) or Subscription (paid versions) section changes to allow renewal.

So yes you have to wait for the interface to change before you can renew the registration/Subscription.