40 m is not always the seabed although it can be. Downcurrent is irrelevant to the post as it can happen anywhere at anytime and at any depth. I have plenty of gas, my buddy is watching me and I am watching her. If a down current happens, I (theoritically) know how to react but I have never experienced down currents yet. And I have never noticeably experienced narcosis.
I don't think down current is irrelevant. If you experience a down current at 60 feet (for example), you are likely to be able to deal with it before exceeding your limits. Plus, you're likely to still have buddies nearby. If you experience that at 130 feet/40 meters, now you've been pulled down past your limits for sure. Worse that there is no help since you're down there alone. If that happens, will anybody be able to assist you if necessary? Will you have enough air to do a deco stop when you exceed your NDL? It's a big risk to begin with, but even bigger since you're separating from your buddies.
Don't get me wrong, I happen to love diving deep. I don't know what the lure is, but I love it! Plus, I have really good gas consumption (and my buddy breathes thru gas much faster than I), so if I dive deeper than my buddy (husband), I even us out a bit. That said, I'd never just descend on my own in order to reach 130 ft. It's too risky...not only for me, but for anyone who may need to assist or rescue me.
My deepest dive was to 140 ft (42.67 meters) at the Great Blue Hole. That was in a group with a guide. (IIRC, a guide is required to dive there.) The dive was planned to include a stop at 60 feet and another at 20 feet. It was amazing, but also occurred with 17 other divers, everyone keeping an eye out for any diver who may experience issues like narcosis. I loved the depth, though don't ask me why. There isn't a lot to see down there, but the formations are kind of neat to see. I would never have gone to that depth alone...nor would I go to 40 meters alone. ETA: Also, I wasn't on air, but on nitrox 25.