I am a guy so sorry for posting in your forum, but, I saw the title of this thread and thought I might have some knowledge. I find that the salt does more damage than humidity. I am assuming that by extended trip you mean ocean and not lake sailing. The salt will wreak havoc on any metal hardware (tuning machine heads)
I have a cheaper but decent sounding Epiphone that I call my beach guitar. I bring it and sometimes leave it on the boat. I take it camping and, yes, to the beach.
I leave the expensive babies at home.