In 1978 or around that time, I ran out of air while diving the wall off Cat Cay (ok, honestly the gauge showed 200 lbs and the reg was still breathing). When it stopped breathing it was still deeper than I could have made a free ascent. While equipment and ideas available back then were different, doubles were an option, but this was just going to be a "bounce". I was diving a steel 72 and a apprx. 6cu.ft. pony. During that time it was normal to dive w/o an octo., so the pony was "really taking precautions". A couple of weeks before this dive, Ed the owner of the dive shop I frequented gave me this pony tank...a gift!
Bottom line: I really got narced and scr*wed up, past where you'd expect a second chance. The pony tank was my second chance.
If I were to do a deep dive again (not likely), I would definitely undergo modern technical training. Still, at this time, I can see a place for a pony during deeper recreational dives.