Boy, tough question, one many of us have asked at various times. I thought I wanted to ride packed trails, gravel and scoot around the campground. I purchase a comfort bike, like the paved rails to trails so up graded to a Trek 7.5 (great bike but a bit too big), with the FX I discovered the road and again upgraded! I love my carbon rode bike!
Last month I added a hard tail mountain bike to the mix so I could ride a packed gravel trail on a vacation trip. The other day I actually rode it on a real mountain bike trail too. I look forward to scooting around the campground with it also.
I guess what I'm saying, this can be an evolving venture. When I started riding I could never have imagined I would one day ride long distances on busy roads. We used to load up the bikes and take them to the paved trails, now we ride to the trail. We've completed two STPs.
It's so hard to know where this journey will take you. Follow your heart and don't be too practical, all the upgrades can be expensive over time! Neither of my first two bikes turned out to be the "do everything" bikes I hoped the would be. And since DH and I ride together, all purchases have been Times Two!
As far as your advanced age, no worries! Your a young pup compared to many of the ladies here! Plus you already ride a road bike.
Sounds like you might like a "go fast", drop handle bar road bike for organized rides. I will say, we did ride 60 mile rides a few times on FXs, but the drop bars really are more comfortable.
Good luck and have fun!
From the dark side of 59!
2011 Specialized Ruby Comp
2015 Giant Liv Tempt 3