It's really not that difficult, the chains are there to assist the referee in determining when the LTG has been accomplished. If there is the slightest bit of doubt, on the part of the Referee, he should absolutely and always eliminate that doubt by measuring.
When there is no doubt, either way, there is no reason to measure. It's not about getting an extra break in the action, convincing a coach one way or the other. Coaches only need to be informed, being convinced is immaterial and is not a purpose of measuring. The only person who needs to be convinced is the Referee, and he has the absolute and only say as to when he feels a measurement is necessary.
Having said that, Referee's also get to choose when, and about what, they want to make decisions without using all the tools at their disposal. A sensible standard is, when there is ANY (whatsoever) doubt, it makes sense to use the chains so all doubt is removed whenever appropriate throughout the game. When there is NO (whatsoever) doubt in the Referee's mind, there is no need to measure regardless of the situation, whenever throughout the game.
Anyone, other than the Referee, who thinks he has some right to have a measurementdone, is simply WRONG.