Neil has earned it. He gave 40+ years of his life to the craft, and was widely recognized as one of the best if not the best. If he wants to retire and ride his motorcycle and/or write books and/or just chill with his family for the rest of his life, that's fine with me. Sure, I'd love to hear more from him and from Rush, but if it's not gonna happen, it's not gonna happen.
I totally agree with it and I think the bolded part above is the only and the real motive for Neil to not want to continue with Rush anymore. Although it has been said that he is having physical issues (and I believe they really exist at least, at some extent), I guess this is kind of Neil giving some "acceptable justifying" for the Rush fans for his retirement. From what I recall (and if I understood right, my english isn't very good
), if you saw the "Time Stand Still" docummentary, at some point, the guy who was the Neil's partner in his motocycle's rides, said that Neil, a lot of times, rode the motorcycle for 8 hours (or something like that) before a show at the evening of the same day. Well, if you are around your 60's and do that, probably you will have some pain in almost all your body during your perfomance on drums in a 2,5 hour show.
I guess this happens even if you are at your 20's!
By the way, IMO that docummentary really shows that Neil already was a bit distant from the band, not from Alex or Ged in a personal level, but from what represents to be in a band or in the music industry.
Anyway, Neil or anyone has the right to enjoy life the best way he/she thinks so. Rush made great music and shows and divided this with us, making our lives much better, so we are quite even I think!