I'm big into lifting and even at 43 I find I've had to do a lot of work on my programming as recovery seems to be the biggest issue now. In my 20's it was easy to go 5-6 days per week and maybe take just a day off between hitting the same muscle groups and now I can do 5 day per week but the days have to be planned more where I make sure I'm not coming back to a muscle group for at least 2 days. A Monday upper, Tuedsay lower, Wednesday rest, Thursday push, Friday pull, Saturday legs, and Sunday rest works best for me now.