i'm 52, and currently run a 4 day split with one day off. i'm on cycle. here's the detail:

day1: Shoulders/traps
day2: back/bi
day3: rest
day4: chest/tri
day5: legs

sometimes i'll swap day2 and day3.

without the rest day i am definitely overtraining. with one rest day, i'm ok. i've experimented with 2 days rest, but have a hard time doing it for mental reasons - i feel like i'm losing mass/strength. joints seem to be able to tolerate my current protocol.

my workouts are HIT oriented. 6-8 exercises/workout, 2 working double drop sets per exercise. done in less than 1.25 hour. cardio is about 3-4 days/week for 30 minutes post lifting.

i think workouts are very person dependent at 50 and over; we all have various issues and our rate of recoveries can vary widely. so... try one or more of the responses here and then adjust for what works sustainably for you.