it would make snese that 3 selections would make more money. You are hitting on 3 more taste buds! Not experienced though.
Having triples in your fleet may not be a bad thing but you have to remember how to use them. They are not suitable for a lot of locations. Your best bet is to invest in quality single head machines. That way you can simply put 3 together on one stand if you find a location that would merit a triple.