Maybe I am hallucinating, but I thought before, you could call the Rube once a day by using an essence of rubeweed, regardless of how long it's been since the last time you traded. I just traded with him at the end of one day, then tried to imbibe the essence after the new day started, but the option is greyed out and the text above it says "You've recently traded with the Rube. Don't wear out your welcome!"
Is this new? I swear I've done this in the past and didn't get the "don't wear out your welcome" message...