Hi. I am an 8-time alum (and about your age) and have gone solo each time. I frequently spend time on my own before or after a tour. I love the excitement of being on my own, but I also really value having the option of company when I join the tour, and, sometimes, when I meet up with the tour after a few days on my own, I feel the real vacation has begun. I don't have to worry about travel connections, etc. Bus goes on the bottom of the bus and it's all good.
For me, each tour has been different in that sometimes I find myself making friends with couples and sometimes with singles. I like having time to myself and, when possible on some tours there is the opportunity for a "day off", I take it. I always pay the single supplement as I am a reader and value my evening private time. Generally, though, even the tour members I end up knowing least, for one reason or another, I find some connection with since we become part of the same group. I have met a few grumps, but very few.
One last thing: every RS trip involving a bus/coach, has had enough room for each traveler to have an entire two-seat area to him or herself, if s/he chose. And most people do choose to have some space at some time, travel partner or no. I never would have imagined this as a feature or factor in my enjoyment, but now, I sure do love my bus space.
If you take an RS tour, enjoy.