What age did men in ancient Greece stop going to war?

Answer 1

In earlier times the general military age was 18 to 45, however boys and older men could be called out as a final resort in defence of the city.

As the empire expanded and expeditionary forces and garrisons required extended service, it became until called out for the duration of the campaign. This led eventually (particularly after the late 2nd Century BCE when the non-propertied class was enlisted to match the numbers of the German migration) to longer term service leading to a professional army of volunteers, whose term of service varied, first 16 years, then 20 years and in the later Empire, 26 years. Even these were extended during severe contingencies, which caused mutinies from time to time.

There were nuances, such as the latter part of the service being classed as veteran (on lighter duties), and differentiation between city cohorts, preatorian cohorts, naval and other specialised service. Auxiliaries often had a different length of service.

So there was no specific retirement age, as it depended on the era and the age you enlisted.

Answer 2

The age for expeditionary forces was 45. For defence of their territory all ages turned out.

There is a record of an invasion of Athens by the main Corinthian army while the Athenian army was away on a campaign. The Athenian old men, the youths and the resident aliens turned out and repelled them. When the defeated got back to Corinth, the old men there jeered them unbearably so they set out again. This time the Athenian olds and bolds trapped them in some ravines and there was a considerable slaughter.

So the answer is never when it was defence of their city.