You repeated some work in there, so how about this?

```
(function() {
	var $ageSlider = $('#age_slider');
	if(!$ageSlider.length) return;

	var ageSetter = function() {
		var value = $ageSlider.val();
		$('#max_hours').html(value + ' hour(s)');
		$('#id_render_max_age').val(value*3600);
	};

	$ageSlider.on('change', ageSetter);
	ageSetter();
})();
```