This inspired some thoughts about big words--words that are 1.5 feet in length or longer. (Sesqui = 1.5. Pedalian = relating to feet.)
I think that it depends upon what you got for your $5. The first consideration when contemplating long word use should be introspection: Don't be a Dogberry. In Much Ado, Shakespeare's Dogberry is an ass, because he uses words whose meanings he does not understand.
So, you've heard the word "loquaciousness" and you think it's a good fit for your writing. But are you really sure you know what it means? If you have to run to the dictionary, stop. You don't know it well enough to use it.
Some times much speaking is not loquaciousness and do you know when that is? The word must fit better than a square peg in a square hole. It must be right.
If you've read the word in only one place, don't use it. If you've never encountered it in conversation, don't use it. Sesquipedalian loquaciousness must be reserved to that subset of your vernacular on which you stand most firmly.
I regard words as semantic legos that one strings together to express thoughts in sentences and paragraphs. Most times the simple retangular bricks do the trick. This argues for the predominance of homely words. You can get the most semantic bang for the vernacular buck with homely words.
Finally, let's turn our attention from the writer and what s/he knows to the reader and what s/he knows. If your reader is online and only a few clicks away from a google search, that's an entirely different thing than if your reader is OFFline and at least a few klicks (as in kilometers) from the nearest dictionary.
Really, really smart and important people have no idea what sesquipedalian means. And only people with some kind of weird word fetish can get as far as "something about 1.5 foot." (This is why you want your kids to study Latin in school.) If you seriously expect your reader to know a long word, it had better be with the awareness that you--the writer--are crazy, and they--your readers--are normal.
I am a hopeless pedant and I thank you all for tolerating me.
The writer should build the majority of his prose around homely words that everyone understands. And when s/he puts in a less-common word, context should provide effective clues as to its meaning.
Take vernacular, a word that drove me to the dictionary when I was younger. The phrase "that subset of your vernacular" can clue the careful reader that something with a subset is also a set. We're talking about words, so it's a set of words. And I said, "your vernacular" which means it's something you possess. So, vernacular is the set of words you use.
After peppering this note with all these foot-and-a-half-long words, I hope I haven't made a Dogberry of myself.