For various reasons, over twenty years ago I stopped singing regularly
I restarted again about four/five years ago, and found I had lost a number of my songs, my pitch had reduced and I could no longer manage ones that needed 'hard' tones without bursting into coughing fits
The length of time I could spend without having a break had also reduced considerably
Luckily, I had been introduced to exercises - (voice, singing and relaxation) - that had enabled me to find my 'natural' physical voice'
After a few months I had most of my old songs back and now can sing for as long as people will tolerate my doing so   
Your voice is a toolbox with which you carve out your art - keep the tools in good order and (unless you haven't developed physical problems), there is no reason why you can't go on creating with it indefinitely.
I was persuaded quite early that you first need to find the voice that comes natural to you, then, which work and exercises, you push out the boundaries to as far as you need to take it.
I believe that relaxation is the least to most problems - uncontrolled tension not only limits the breathring, but can actually damage the voive

I believe that going to most 'voice' specialists is a waste of time and, given the state of the Health services, no hard-pressed doctor will be willing to give their time to something as 'trivial' ass singing
Many of us were told when young that we "couldn't sing", yet, found that we had no problems when we tried our hands at folk songs
I believe the 'natural' voice common to folk singing is considered "ugly' by the art establishment and by many teachers (it was in my youth)
If you can't make a half decent job of 'Cherry Ripe' as a baritone or a tenor, you'll never make a singer
Good luck
Jim Carroll