"Mac...I think (in hindsight) 25 would be a good starting point."
I noticed from an earlier post that you became a cop "as soon as you could". That's why the hindsight.
A salesman has plenty of experience as a buyer. He brings that to his job. An engineer spends a good bit of his life dealing with problems[think automobile] caused by other engineers. Doctors get sick and hurt.
A cop who's entire adult life has been as a cop, has never seen the other side "of the counter". He's never been subjected to the arrogance and B.S. some cops display on a regular basis, or been physically mistreated AFTER the cuffs are on, just for fun.
You guys inhabit a world pretty much immune from mistreatment by the others in your profession.
I can't think of another field of employment like that.
Hell, even Lawyers get sued by other Lawyers.