could i go 60-90 seconds full on??? I don't know... but my answer is probably not.  I studied Tracy's Kenpo, an American Kenpo based off the Ed Parker system.  I am now in my late 50's and all sorts of bodily damage and stuff.  I still practice daily movements but realize in a real situation I may be extremely limited if I don't or cannot end it quickly.  my new favorite saying is , I was born with a six pack of whoop ass, I now have only a couple cans left...

what are ya'll doing at an older age with muscle deterioration and nerve damage to keep yourself at least in the game for longer than a minute or two...

and yes I'm a realist... I know what I am capable of, and what my limit may be...  thanks

Cardio is key, so is some form of strength training.  Pick up a kettlebell or two and watch a bunch of videos on how to use them.  

You can get both done in a short period of time with them. Think HIIT.

Circuit training may be what you are looking for.  

Or you could do a couple rounds of hitting a heavy bag, then rest, and repeat until exhaustion.

Sorry to dig this back up again, but I'm looking into American Kenpo.   Do you still train?