Conciseness is developed through experience provided that there's a desire to be concise. All LIIs over the age of thirty that I've met were either concise, terse or silent. I tend to consider too much data so if I were to express my thoughts about complex issues without due consideration, it would likely be incoherent to others. I dread being swept up into important conversations for which I'm unprepared. All Ijs and Eps need time away (in sort of mental isolation) in order to put their thoughts in order; they're certainly not as naturally adept at real-time expression as are Ejs or to a lesser extent Ips. Now, I've met many Eps and other Ijs who didn't care whether or not they were concise and so tended to ramble whereas I haven't met any mature LIIs like that because they tend to be perfectionists - but I'm certain that they must exist. Note that younger LIIs can be rather impatient to get things out and also not consider the impact of their words; but eventually, most realize that they really shine when they ponder quite some time before texting or opening their mouth.....
a.k.a. I/O