Robert from the New Push Ups forum is a great person to learn from for longevity in fitness and health. He goes by Atlas's," Train Don't Strain" saying. This is no knock on Greg or Gary because they are very good guys to learn from also. I forget how old Robert is but I do know he's in his 70's. He Keeps It Simple and stays Consistent. That's the secret to Life Long Fitness and Health.
https://www.tapatalk.com/groups/newpushups/consistency-is-what-counts-t1208.html#p11542
Here is something he wrote:
Consistency is the key to success in fitness or any endeavor. You can jump from program to program, try this and that, to find a fit for yourself. But then you must be consistent to give your selected program a chance to be successful. I am back from a long vacation where I put on quite a few pounds, alas, gaining back all the weight I had worked so hard to rid myself of previously. But now the pounds are coming off, I am eating sensibly, and doing bodyweight circuits of high knees, squats, crunches, and pushups every morning, along with a 30 minute brisk walk. This is doing it for me! Why change? I will stick with this one, as it is doable and enjoyable for me, thus I have found my fit, now I must consistently follow through. So, at 77, I don't need to read any more fitness books, or follow some "guru's" program. Eureka, I have found it, I just need to consistently keep at it.
I like this philosophy too; therefore, I use DT and Iso exercises with a stick and add some Yoga asanas. Unfortunately, my joints cannot tolerate multiple bodyweight reps.