Nearly 70? Bloody hell! I’m a mere spring chicken at 40 and regularly feel broken after a days graft. Suppose being retired you have time on your side. I’m juggling my build with a job and 2 young kids. More than I can take some times.
Ha, nearly 70 but still playing in a Rock Band!! Yes, I don't know how I'd have done all that if I was still working. In your case it will be harder for you...but you will get there. Just look back -on when you started and Remember to take lot's of Photograph's.