Wow. Many people on this forum have been through hell and back.
I had a kidney transplant at 32 (now 40) and I am heavily immune suppressed. I will also, likely, need another transplant to make it my life expectancy, 65 years old.
I figure, pretty much, the lot of reptiles I have now is it, unless something drastically changes health wise. Katie (my wife) and friends have plans if something happens to be suddenly, but otherwise, I figure I should outlive the current crew by a little and would find homes for any residual residents as I got older/sicker.
Going back to the OP - and what has been said here - if you can care for the animal(s) for a while and give them good homes and potentially outlive them, go for it. Otherwise, have a backup plan in case something happens.
However, I do not think you should keep yourself from having a reptile(s) because of age.
One other thing to point out is reptiles will ultimately be happy with proper husbandry and food. They don't really get attached to their owners and would do fine being re-homed if necessary. It's not like a dog who will miss his/her family if they pass, re-home them, etc.