Pro Dive offers Nitrox free! And to some, diving Nitrox is less tiresome.
Once upon a time I had to dive 41 days in a row as a DM while 50 years old +. Hell, I was tired! Staff said try nitrox and I did.
Didn't make any difference to me at all, so as far as I am concerned the feel feel good part is a myth. Not to say others can't feel it.
Dave