After maturation, each time someone burns, an external call NotionalV2.settleAccount(address(this)); is made. Even if it's a noop, it would be cheaper to have a local variable to store this and eventually skip the call as it needs to be done only once.
[Gas - 01] - Settling of account could be saved locally
https://github.com/code-423n4/2022-06-notional-coop/blob/6f8c325f604e2576e2fe257b6b57892ca181509a/notional-wrapped-fcash/contracts/wfCashLogic.sol#L221
After maturation, each time someone burns, an external call
NotionalV2.settleAccount(address(this));
is made. Even if it's a noop, it would be cheaper to have a local variable to store this and eventually skip the call as it needs to be done only once.