On my last two road trips I took my two Nikons and their associated lenses and my 5x4 kit with its lenses. I did not take a single photo with either Nikon, even though they travelled 9000km to be with me.
It seems I'm addicted to using the best quality equipment I have at hand. Why shoot on 35mm? If it's worth capturing, it's worth doing it properly. The Nikons are staying at home next time.
My advice? Shoot with the biggest film you can carry. Life's too short to regret shooting on tiny film.