I think that for a many of us more mature guys we worry that we are quickly approaching our "sell by date". I know that I certainly felt that way a couple of years ago.
I'm pretty much exactly 10 years younger than you. I've got between 12 and 20 more working years available to me. Virility - I can't comment on - but I presume that everything still works - but for how long without chemical intervention is anyone's guess.
Part of my "guy" make-up is my vision of myself as a provider. I can do that pretty well now, but once I retire, my pension will be modest.
A lot of mature guys are also looking for a home-maker, a harlot or a nurse and depending on how well they can manage on their own may be looking to fill that job quickly.
One thing that worries me is that in my two lifetime serious relationships I was chased and love-bombed into submission and got "serious" in a matter of days. I now know through painful experience and through study that this isn't "normal" or even healthy - but many people do believe in "love at first sight" and soul-mates. I remember making a young lady bartender quite sad when I told her that I no longer believe in soul-mates.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells