For the Style Nazis. What makes an Old Ale Old?
It's in the name. Old
, ie., well aged.
All of the things Ron mentioned are important. Also, to some degree the strength also factors in but primarily and infinitely more importantly
(at least if you're talking authenticity), is prolonged aging
, which introduces other flavor characteristics.
Style definitions more and more seem to be an arbitrary free-for-all these days, often with no historical basis. You can brew a recipe for "Old Ale" and start drinking it in 6 weeks and experience some of the characteristics and if well made it will taste qyite good at that age. But that would only be a quasi Old Ale. You'd only be experiencing part of the show.
I'm not a 'style nazi' by any stretch...just plenty opinionated and a bit of a history buff.
But it would seem to me that the bottom line is that long aging is the final essential (and arguably most important aspect) of the style.