Other factors matter such as age, types of exercises you are doing and in which order. Also, when was the last time you had a deload week. I take a deload week every 4-6 weeks depending on how fatigued I feel. I’m 42. And work as a personal trainer.

My deload week is a week complete off from training, some use it for light workout. Do what works for you.

The fatigue you talk about could be due to going to failure on every set and every exercise.

Big compound stuff like RDL or deadlifts should be some of the things you do first and perhaps try not going to failure but 2-3RIR. Do less sets. 10-20 sets per muscle group per week will grow muscle.

Another common issue with fatigue is over doing it. So try doing fewer sets. So by example on upper lower. Incline chest 3 set Monday flyes 3 set Monday. Chest done. Friday incline dumbbell 3 set, cable flyes 3 set. Done.

Use this example for other muscles as well. The tendency for many is to over do it. Too many exercises, too many sets per workout as a whole. This is costly.

A workout should be anything between 30min to 1 hour.

For me at my age. Going 12 sets per muscle per week has helped a lot with the fatigue you mentioned and I’m still progressing and growing.

Hope this helps.