I didn't really start having any success as a weight lifter (success defined as actually adding muscle mass to my body)
until I was 40. So my lifting style and philosophies are shaped by that. Clearly they are different than when I was younger, but for me, different in that I was NOT able to successfully build muscle as a younger man.
Here is a fantastic article written by a guy that was a champion body builder at 20, and his views on how his lifting style and weight training program has had to change as he turned 40.
What's important to get from this is that I and even he, as a former pro, can still add mass well into middle age. BTW, I do DO things at 52 that people half my age would have struggled with 20 years ago. We have come a long way.......................