The older you get, the more important strength-training becomes to maintain full functionality. And while it may be most important for women (to deter osteoporosis), all men want to be stronger.
Our recommendation is that 1/3 of fitness training/conditioning (ie about 2 hrs/wk) be basic weight-training with gradually-increasing weights as tolerated. (Our simple plan is 2 hrs mixed cardio, 2 hrs calisthenics, 2 hrs weights, even though there is plenty of overlap to make it all synergistic.)
Here's why: