Weight training and age...
I can see there are some very knowledgeable weight trainers on this forum.
One thing I’d like to add…
Assuming that proper diet, sleep and correct training is adhered to, younger trainers can tolerate more sets, frequency and recover much better than older trainers.
When I was 20 I could train 5-6 days a week, fully recover and grow with no problems. Now that I am in my late 30’s I cannot do this. I feel fortunate to be able to train hard 4 days a week and make progress. Now my main concern is to train as hard as possible without getting hurt :)
It’s also much easier to get fat when you’re older. When I was in my teens and early twenties, I could eat junk foods 3-4 times a day and not get fat. If I tried this now I’d resemble the goodyear blimp. Now I must implement 2-3 days of cardio to keep my waist down. I love food way too much to be on a very strict diet.
Morale of the story… Getting old sucks!
Observe... learn from other people's mistakes.