Excluding most hereditary diseases, exercising will not only make you healthier, but it will prevent (for the most part) any of your worries. If I don't exercise I become really stiff almost overnight, (I'm 59) and 30 minutes a day on a treadmill, and a few times a week on a elliptical machine, I can (and do) what I did when I was 20. I can get by fine with 3 times per week. (I'm not overweight) Yesterday I spent 4 hours trudging along the sandy sloped riverbanks of our local river, the sand made it really hard to keep my footing, and the many, many large limbs and trees I had to step and climb over also made it all the more hard. If I didn't exercise, there is no way I could do that, well, maybe once, then they'd have to come and get me.
Also, I walked in the woods the other part, and I walked 2 miles total doing this, it was hard, and later I was tired, but it didn't get the best of me, I wasn't even out of breath! heheh
I see people walking for their health all of the time, but the main thing I see is that they are walking slowly, which is better than nothing, but that is not what a person needs to do, they need to get their heart rate up, cardio, all of that stuff.
If you do this already right now, then by the time you're my age, or older, you'll be fine. When I was in my 40's, I was in my prime, (without exercising daily, my outdoor life was busy) mentally and physically, your youth will leave you if you don't exercise, real quick as you approach 50.
Now, if I bend down, my knees don't creak, my back isn't going out, (and it did for years due to lack of exercise) and the age problem at least mobility-wise, it's not a problem.
I also do sit-ups and leg presses on a Total Gym before I exercise, when I am on top of it, I do 600 leg presses, (Sometimes only 50, so I can and will slack off) and I always do 100 sit-ups. This is on an incline, so it is easier to do, and not as hard, although, it's still very hard. heheh
(I do from time to time slack off from exercising, and I get 'old' again, so I am not a health nut, just someone that wants to stick around doing what I like to do a little longer, that's all)
Really, I know how hard it is to commit, but I only wish I knew now, what I should've realized then, that staying healthy at a younger age, before it 'gets you' later.
This, along with the aforementioned posts will make it to where you shouldn't have a problem at all.
I definitely don't want to come off like I am perfect, or 'one of those' people. My back was always "going out", that is, until I started exercising, now, it does it only rarely, if I abuse it, but it was common for me to miss work due to it, I didn't realize then the power of exercising. Also, I used to smoke, (almost 40 years) and I am a type II diabetic now, but so far, I am in really good shape, anything could happen at any time from my past catching up with me, but at least I feel as though I'm making headway. 
Randy
MakeMeShutter wrote in post #13663260
As I write this, I am thinking about the future.
I imagine a day when I will be unable to get around like I do today due to health and age.
I am 44 as I write this, shoot with many older photographers that are quickly approaching that point.
Any advice from others as to how to overcome this sort of inevitable challenge?
Tips or ideas to continue the persuit of photography at that point.