There are exceptions to every rule, including Jack's favorite 10 yr rule.....and after all, most of us are exceptional, aren't we?
I had my first big exacerbation in 1975 with SX back to 1964. I didn't become SPMS until around 1998. I'm not in a WC, although, I use my scooter most of the time.
I think my age is now in the SP stage, too, though.