Why do you save your LB?

[PArcher]

Ultimately, it depends on the fight.

Dungeons, I'll use it usually when I feel like it; it doesn't matter. It just filled both bars? Sure, I'll pop it (assuming no mechanics that could kill me)

Trials...it varies.

Ifrit HM - First LB (at Nails) is for a caster, unless there's no caster (which then LB to get rid of one Nail). After Nails I'll LB when we're near the end and the healers don't need it.
Garuda HM - Wait til after I know that the healers won't need it (DF only...a pre-made with people I know LB goes off when its best to do so, which depends on DPS and timing)
Titan HM - Can be used in the Heart Phase if DPS is lower. Then near the end of post-heart...again, after its known healers won't need it and you know you won't die during casting

Ultima HM - Tank LB. Just forget the LB exists

Garuda EX - Has to be during a feather phase near the end. Should be used to kill (or leave a sliver of HP to DoT-kill) to avoid another Sisters phase. Tank LB can be used if Spiny is killed early...but I've only seen it succeed on a feather-phase Spiny, not a Sisters Spiny
Titan EX - Caster LB on adds is best IMO. But if you don't do it, LB3 after the Gaols after the second adds (likely will land during stomps)
Ifrit HM - Third Nail Phase. You likely won't have it back after, but if you do then just use at 1

Coil 1-5 - Completely depends on group and your strategies. There are so many ways to use LB and its completely on the group.

Notice a pattern? Holding the LB as a safety for healers. Dead people do no DPS/Healing/Tanking, and a Healer LB3 can save a group should things go wrong.


EDIT: Forgot CT. Lol, just use it whenever. Who cares.