In this episode of AskHistorians Aloud, we talk about conscription in the Ancient Greek world. Iphikrates answers "I'm a farmer in 500 BC in a typical Greek city-state. How often will I get called to mobilize for a battle?"

 

Link to answer: here.

 

Update: Someone has pointed out that a bit of the outro got recorded over the answer! Terribly sorry about that. Here is the missing text:

How much of the time was wartime is an open question. But even during the Peloponnesian War, there were several uneventful years, in which Sparta did not call out the levy of the Peloponnesian League and Athens had only men from the Lists in various expeditionary forces. In such times you, as a regular farmer, might escape military duty altogether. And if your city-state wasn't a member of the League or a subject of the Athenian Empire, you might be fighting your own petty wars, but otherwise you'd be left mostly alone.

It is anyone's guess how often you would actually be involved in a battle. Given all the factors I've mentioned, regardless of your city-state's foreign policy, I am of the opinion that the answer is probably closer to "once or twice in a lifetime" than "every year". However, given the lack of comprehensive source coverage, and the fact that historical accounts sometimes casually mention several battles in the course of a single campaign, my guess may well be wildly off the mark.