I try to use as much vocabulary as possible, but I also will rarely go out of my way to make an opportunity to do so.
In the event I can work in a word less frequently heard, I like to, but it's not a big deal for me. I'd rather try and simply sound natural. Sometimes, when you appear to be attempting to use as many words as possible, you sound far less sincere and look like a snobbish dick.
But if you use grammar correctly, in a conversational manner in a way that MOST SUCCINCTLY but MOST ACCURATELY describes that which you wish to inform someone, it will appear to flow and feel familiar without alienating anyone.
I've never felt like anyone thought me a dick for using rarer vocabulary, but I've been known to feel that way of others when it feels less than sincere and conversational. When it sounds/looks like an attempt to prove mettle/worth, it makes it look like they are condescending and wish to inform others of how much better they are.
That said, while I enjoy reading and enjoying learning as much as possible, more of my knowledge seems to be taking in random facts that are presented conversationally, as opposed to seeing a varied and dynamic vocabulary. So I don't have a large vocabulary, not of the range, at least, that I wish I had attained by this point in my life. Which, however, does make me feel good, because I've only recently passed the quarter centenarian mark. 😉 I've known many my age and younger who could wipe the floor with me using grammar, but I've also always felt bad for them. 😛