The only place I use it consistently is after the nails are dead in HM Ifrit. After using LB3 on the nails, killing them all will build the limit back up to at least LB2 (sometimes you can get LB3) before he uses Hellfire. It mitigates a large amount of the damage, and you still have enough time to re-build back to LB3 again by the time DPS need to finish him off.