Skyward Sword is the lengthiest Zelda game out there, bar Breath of the Wild (which can be a lot shorter if you skip the main quests). Well, at least for me it was. Don't know how it'd feel that way for you.
Depends on how you measure it I suppose. Due to my Wii breaking before the game came out, the only time I've played it was when I borrowed my sister's for a couple of weeks. Even without using a guide, I'd found all the heart containers and most of the secrets by the time I'd sent it back. Conversely, I played Twilight Princess a lot longer and never got particularly close to feeling like I'd found everything.