A forever buyout, beside the same work licensed and renewed while the ad keeps running.
A renewal only happens if the video is working. A brand keeps paying to run an ad while it earns more than it costs, so a licence that renews pays you again exactly when the video has proved itself. If it flops, they stop, and you've lost nothing you'd have kept with forever. That's why the comparison above is the fee against the renewals, not the fee against nothing.
The usage fee is yours to set. There's no official rate for UGC usage. Social Creator Club's UK rates guide puts paid ad use at 25–50% of the fee for 30–90 days and forever rights at 100–200%; treat those as a starting point to argue from, not a price list.
Forever isn't always wrong. Organic use on the brand's own channels is worth far less than paid ads, and a buyout priced at or above the licensed figure is a fair deal. What to say instead, and what to check in the contract, is in the guide to forever usage.