Well if you tax what they already have on them. They can go for days. Not sure how many but I know at one point there were ones that went across the oceans. Not sure if they still do as its unpopular to have ones where you can’t disembark on see places regularly thats not the ship itself. Also not sure how far the monstroseties they have now can go with the waterparks on board. I suppose it could be farther with the size allowing for more fuel but maybe less given all the space used for crazy things like zip lines or whatever.