I've written previously about Napoleonic era drummers (and musicians generally) here.

While young drummers weren't unknown in Napoleonic armies, mature men were preferred. Drummers had to carry heavier loads than regular soldiers on campaign - a French drummer's normal load was 2kg (4lbs) heavier than that of a regular soldier - and they had to keep up with lightly loaded officers during a battle. Drummers also needed to keep their heads under fire and beat out signals correctly. The French army set a minimum age of 16 for drummers and other armies were similar - the average age of the drummers of the British 2/73rd foot at Waterloo was 23, with the youngest being 19.