Honestly its based on a number of variables usually shift patterns, 2-4 i would say.

at 69 i agree i keep things moderate.isometrics are the main program

Agree, when we start aging, the decrease of our flexibility becomes a main problem. To slow this process, I added to my regular strength exercises several mobility exercises with a stick and Yoga asanas. It helps.

With tension style exercise it is possible to do the same exercises every day. You moderate the tension from day to day and you don't have wear on the joints. With weights and body weight training, you've got wear on the joints. The shoulders, the hips, the lower back, and the knees become focal points for wear and tear over time. You can get away with a lot for a lot of years, but there comes a time where you pay the piper. As you age, and I am in my late fifties, your mobility, balance and flexibility become harder to maintain. That is why I believe you need to rotate your body weight exercises around during the course of a week.

In general, I stick to the same routine and perform it 5-7 times/week.

Yeah two times a week seems to be what works for me also. I would say unless I do full body workouts with minumal exercises. Right now I'm doing a 10 week experiment with volume with a Push/Pull/Legs & Abs split. Each is done twice a week.

For me, right now it is sit-ups/push-ups two days, step-ups and pull-ups two days, and Hindu Push-ups, Jack Knives and Free Hand Squats two days. I do isometrics for the arms and waist on push-up days, isometrics for the legs and back on pull-ups day, and isometrics for the neck and shoulders on Hindu push-up days. At this stage of life I recover better if I don't do the same movements more than twice a week.