I'd say that you're never too old - there's a 'youth culture' in a lot of the west that seems to imply that once you hit your 60s you're suddenly good for nothing.

Someone that old could be put through an alternate basic training, and put to work teaching people whatever it was they spent their life doing. If you've managed to survive to that age, you must have /some/ skills.

I suspect it's the same in the US, but here at least we're facing a massively ageing population, and a lot of the previous social prejudices about older people are going to have to change, since it's not going to be optional: people /are/ /going/ to have to work until they're older, and older people are going to comprise a higher percentage of the workforce than before. Companies need to adapt and see where they can use people with more experience.

If it's good enough for the corporate world, it'll do for the military. Sure, 60 year old (or even 50 year old) recruits aren't going to do much good on the battlefield, but that guy who spent his working life as a mechanic might be useful when it comes to servicing tanks, and the 50 year old school dinner lady will fit in just fine at the canteen.