DCL's has not yet done a cruise longer than 7 days, so we can't be sure what they might do for the 10-day Christmas cruise or the 14-day canal transit cruises. But, on the 7-day cruises, they do vary things a bit at both the restaurants and the theater. In addition to the regular restaurant menus, they have two formal nights, a tropical (eastern) or Mexican (western) Theme night, and another theme night, sometimes called "Small World" or something to that effect. On the theme nights, all three restaurants have the same menu, but you never have a repeat menu on any night during the cruise.
The alternative dining at Topsider's is a nice option, if you don't make it (or don't want to make it) to your assigned dinner. There is sit-down table service, and a dessert buffet. The menu usually includes some of the choices from the dining rooms on that night.
For the shows, in addition to Hercules, Golden Mickeys, and Dreams, they have "Who Wants to be a Mouseketeer?", a welcome aboard variety show, and usually a first-run movie, called a "PremEar at Sea."
I would imagine that they would add to this for their upcoming longer cruises, rather than just recycle the menus and entertainment.