Very curious on us older reefers. I broke past the 60 year old mark and do love this hobby but at what point do you say "I just can't do this anymore "
You don't. And the question, in my opinion, applies to all ages. If we are being honest it comes down to the design and implementation. Why design? Simple answer really, accessibility.
The saying goes 'forest for the trees' comes to mind. We rush in with excitement and too focused on the small details not understanding the big picture. In my opinion. What is the big picture? Age.
When properly set up, and cared for, our reefs will out last us, the hobbyist, and passed down, sold, given away, or in some cases thrown away like leaves in the compost bin.
Hip or knee replacement. Movement and/or weight restrictions. Sciatica nerve damage - back pain and more limitations. Vertigo balance, limitations. Age doesn't care. Something can happen and it may cause limits which will require either a decision such as does it make sense to continue or getting help.
So back to the design and implementation. Creating an environment for the long game reduces some of these issues. A skimmer collection cup is such a simple task but the hip, knee replacement or nerve pain may limit us doing so. Having that same skimmer raised such that we no longer break 90 degree plane, well, lets us continue on with the hobby. Likewise with reducing ladder usage or reaching for things to do routine maintenance. Making things accessible, safely, for day to day maintenance is key.
At the end of the day the design also allows us asking for help or assistance. Even hiring in someone or a maintenance team. Having things laid out and documented as to what goes where or how things work, well, creates less stress for everyone and saves you money if hired out.
A bit of a ramble or rant but hopefully some of it makes sense. I fell into this question after having a hip replaced. Reef tanks, in my opinion, should all be treated as a project regardless of size. Documented and laid out. I know it slows things down and may increase the cost but as the saying goes 'an ounce of prevention is worth a pound of cure'. Easier and cheaper to stop or limit the problem before it starts and fixing it later.
Just my take and your mileage may vary.