I was taught
- under 1/2 scale deflection
and
- flying the required heading (i.e. a stable approach course adjusted for wind)
The fact that ATC requires you to "report established" usually implies that you are within calibration range. And you have identified the morse code, which is unlikely if you are 25 miles out.
Sometimes you want to get the report in nice and early, before somebody else jumps on the radio with their inside leg measurements
I disagree with that. I aviate, I navigate, and if Uncle Tosser bull****s about the weather when 25 NM out, I just let him until he stops. ATC will know that I cannot report localizer established until he's off the frequency.