At 56, I have had my own gym since 2000.
I have progressively lightened the load and focused more on lighter weight, higher volume but what has really helped me is TUT method. Concentrating on super strict form and very slow on the negatives.
since about 2010 I have went and stayed with supersets with about 3-4 minute rests.
I stay off the hard stuff ( Tren, Dbol etc) and stick with basic stuff like Test, Eq, Mast, Primo etc.
I also change up my exercises Monthly.

What are your stats?