I have not yet dropped to a 15-30 second wait between sets. I couldn't even bench press 8 sets x 8 with 115 with a brief wait (30-60 seconds) a couple weeks ago. I am going to try it again soon. The loss of strength after 2-3 low-wait sets is remarkable for me.
I was not timing the wait, but yesterday I quasi-supersetted ~8 rep per leg sets of step-ups with 20 pound dumbbells in each hand with 6-10 rep (broad range) sets of 135 pound trapbar deadlift. I waited about a minute between supersets. I looked around and no one was sweating harder than me on the weight room floor. There were some strong guys in there, not fitness enthusiasts. Like you said Stephenlay, one has to focus on themselves and not the guys military pressing heavy dumbbells or squatting 315+ like I saw yesterday.
I'm sticking with the higher volume for a while and will see how quickly my endurance grows, and hopefully so will rise my strength.
Oh, and Stephenlay, great point about ending the set when the form falters. I found that I had to stay more mentally focused on my form with the low-wait, high-volume sets. I usually ended sets with the sense that I had more in the tank, but a detected loss of stability.