Hi there. I can see where you're coming from with regard to the limit break. In my opinion the limit break should be used at convenient times:

1) During a boss fight (generally only reserved for melee dps. But ranged should execute it if the melee is lacking attention, or there are no melee dps on the team)
2) To pull a boss (if you only have ranged dps)
3) To burn down a large controlled group of trash mobs

Now some people may argue that the limit break should always be kept on cooldown. Whilst I agree that in most circumstances that is a wholesome use of the limit break, I also think that it should be saved if you anticipate that the party is approaching the boss of the dungeon.

Ultimately, executing the limit break at a convenient time, whilst giving sufficient time for the bar to recharge before the boss, seems to be one of the more efficient methods of using this handy tool.