Although I have retired from competing, one of the things I thought of in my 30s and 40s while I played along side the senior division at National league tournaments was, "is that going to be me some day?"
I believe the senior division starts at maybe 55? But you can decide when you want to play in it. In other words, you don't HAVE to enter at 55, that's just when players become eligible.
My thoughts on playing in the senior division have always been this: I'd still be playing the same players that I am now!
The men and women senior divisions have the same players I used to see playing each other 10-20 years ago, and they are just playing each other in a different division.
I admit, I never considered that I would be playing competitive pool into my 60s. I know many close friends that still do and I admire them for still having that fire in their belly! I just didn't imagine still playing another 20-30 years or so back then.
And now that I'm not competing, I am lucky I don't even have to cross that dilemma path now :)