If a ls dissolves then there is nothing you can do about that just bad luck. If the leaders suck or they are not doing what you want in the direction you'd like then be more picky about the ls's you join.
I had 3 ls's in ffxi and they lasted till the end more or less for 7+ years cause I did some research. They had websites, I read the forums, checked out a few of the players or profiles on here. The rules were good, the outline of the ls's activities and goals were there to read.
So if you are burning bridges which means leaving on bad terms then don't. If after all the above I typed turns out to be a bunch of bs and the ls sucks anyway after you join then just say thank you and you appreciate it and leave or just toss the pearl. They'll think you quit playing probably anyway.
Basically stop burning bridges or lower your expectations for a game that is just getting a endgame going and basically a new game overall with lots of returning players.
Check out some of the top ls's on your server on here. Every ls doesn't suck... just sounds more like super bad luck or too picky (or not picky enough?) or whiney.