Bro, that kind of extension is like another game. I dont ever recall any single piece of DLC adding an extra 30 hours to a game. I'm curious to where that expectation is coming from.
Xenoblade games are collosal in size and Nintendo deemed this expansion to be big enough to be released as a standalone game. If they hadn't already sold the expansion pass for €30 since last December, I am sure that Torna would have been at least a €50 game.
A length of 30 hours won't be a problem for Torna. The amount of cutscenes is supposedly close to that of the main game and a new titan got added. Throw in most, if not all, titans from the main game with rearranged content for exploration and 30 hours aren't a lofty goal at all. If Torna is only half as long as the main game, most players will still comfortably cross the 50 hours mark.