No doubt that the Military is a young persons game but on the other hand with better execise/diet/medicine we are staying younger longer and living older. I think the Miltary are missing out on a lot of (a) Maturity and (b) experience by capping the age limits.
The RN used to have a "Promised Man" Scheme where Men could be selected to go until they were 65. I met one of the last these fine Chaps at Collingwood. Lovely old fellow - full of good advice. His duties were Light but a lot of the guys & Girls looked up to him