I recently turned 50 myself.
How much is 'too much' at any age is very individual, but it's true that as we age, recovery and rest become more important.
Your schedule does look tough. Maybe it works for you, but feeling "very tired" and "on the verge of not feeling good" sounds like possible overtraining. Even professional athletes like Martina Navritalova (sp) say they need more recovery as they get older. It's just a fact of life.
I'd like to think that as we age, we not only gain knowedge, but have the wisdom to use that knowledge, and that applies to fitness in that we learn to workout smarter, not necessarily as intensely. That may be changing the sequencing of our workouts (to make sure that we give each body part more rest than when we were in our 30's for example), varying the intensity of our workouts more, including balance and flexibility training by doing some functional fitness type workouts and stretches/yoga, modifying and not trying to keep up with what we 'think' we should be able to do or what other people can do(doing our best, but not pushing ourselves to do what we maybe could have done at 18 with no problem), or even backing off a bit as we get signs that we may be overdoing.
I also think it's important to have specific recovery time, or to 'periodize' your workouts, so even those who can workout 'full tilt' most of the time would benefit from a recovery week (doing lower intensity workouts, more stretches and restorative yoga, some functional stuff).
If the sample schedule you posted is how you work out most of the time, I'd say you'd benefit from a recovery week. Maybe 2 moderate-intensity cardio workouts, 2 functional fitness/core workouts, 2 days of yoga/stretch, and one day completely off.
:7
