Once you get infuriate you'll want to use it for the extra healing. The thing is if you can get away without the +15% healing you might as well spam it all day. On things like Hardmode Ifrit it's best to use when he gets you low and pop infuriate to keep stacks up. If you just got it recently I'd say spam it all the time there's very little low level stuff except maybe Garuda where it makes a noticeable difference.