Based on the design and size of the drag components, high teens, low twenties would be a good place for the reel to operate. There are two steel washers where the heat is generated, heat flows through the drag washers to the spool and from the spool to the air. Some of the heat goes through the shaft and bearings, hopefully, not too much.
High teens/low twenties initial drag (measured) will stop a very large fish. I didn't find a Bluefin between 150 and 200 lbs. that could run more than 200 yards at those settings, usually less.
I think many others that have used the reel will be able to tell you how much abuse above these numbers the reel has withstood.
I've used 665N for the exact purpose you want (AJs around oil rigs). I 2nd what Kidflex posted. I don't think it is possible to raise an AJ fast enough if hooked very deep (over 100') and very close to an oil rig to prevent them from getting in the rig structure if they want to. If you are up close to the rig and hook-up with 150-200' of line out they have a BIG radius to circle back into the rig when you are vertically over them. Just imagine standing on a huge upside down ice cream cone and you can visualize what I am talking about. If you hook-up and quickly move boat away from rig at a 90 degree angle while hanging on and NOT trying to RAISE fish until clear of the rig you stand a much better chance of putting ants in their eyes. This changes the angle of the fight and gets you in clear water. They tend to "panic" when they feel themselves being pulled up. If you just hang on while moving boat to clear water they can be "lead" away from rig and then fight them.
Remember they are "endangered" in the GOM right now, sometimes at the right rig you can only hook up on only every 4 out of 5 drops. PLEASE!!!
I've been leading them away from rigs for years on heavy tackle and live bait but it's an exercise in futility with the toriums and trevalas my boat is outfitted with for jigging. they work fine for snapper and smaller grouper but I want a rig for myself that can put some heat on bigger fish. we try to avoid AJs with jigs b/c we lose so much tackle.
I'm not expecting to go toe to toe with big fish from a dead boat.