Small things add up on the endurance side....I'm in the mortgage/married/father category as well and two things that helped me immensely.
1) Reduce the number of side to side motions...I used to slide off the side, corner, slide back to middle between corners, then slide to the side again. Basically took out the middle part which reduce the number of ass lifts by a 1/3.
2) "Knee to knee"...if you have done all the CSS levels this should be a known drill, by using my inside knee to leverage my butt off the seat and engaging the outside leg on the tank it reduced the amount I had to unweight myself through a leg lift to get the same position.
Still gasping after 5 laps at Chuckwalla, but a quick dive into the pits for 15m of rest and I can go back out instead of being spent for 45m.
I guess a third thing was gripping the tank with both knees for longer, was doing that for braking already but now I use it for acceleration as well and only disengage at the tail end of turn in. Keeps the bar grabbing bad habits at bay, core engaged, and endurance up!