Adding Endurance work to end of workout

Thanks for the replies. I should have said that it’s more to target what I think is my Endurance weakness rather than just boosting TSS but hopefully the 2 will work together. It’s only my 2nd year of structured training. I did SSB 1 + 2 (twice) last year followed by General Build but I always skipped the midweek endurance workout.
Still I worked pretty hard work but I noticed 2 areas for improvement for next season. Maybe you guys can weigh in on this.

  1. I feel that I got so used to intervals where I am going 90 + % for some minutes then resting that I wasn’t very comfortable with long periods of time spent at Endurance / Tempo pace.
    Would adding the endurance steady state work help to address this?
  2. This might make my whole point about adding minutes to my workouts sound counterproductive but I found myself feeling a bit burnt out as I approached my season ending trip to the Alps in September. It was all going well until late July then I felt like I was hitting a brick wall during workouts. Every workout I did was minimum 90 minutes + the usual progression of VO2, Threshold, Sweetspot work.

I don’t think I was far off especially since it was my 1st year but I would like to know how I can put in a similar level of work this year but perhaps adjust the intensity so that I can be fresher for longer into the season?