OOT only took me 2days too complete, Mask of Majora took me the better part of 2 weeks simply because i kept failing at the final challenge and you have to keep going back in time all the time.
Never completed Link to the Past, gave up about 3 dungeons in - it bored me. But then i played OOT as the first Zelda i played
TWW took me 3days, but they included OOT and Master Quest which both took me a good sight longer to complete
the new one hopefully is going to be alot longer because if you think about it they complete remade the originals with the updates, they're the same but still takes a long time to update all of those graphics and animations
so really for that 2years of work it was a new engine, plus around 25 dungeons ... so the new one is probably gonna be pretty huge.
the problem never was the level count, but the fact of the story to go with it - and the design of the world.
You can get away with less if the design is much better... TWW took me a while because you have to travel between the islands so much.
That and i don't think i had the chance to pay AS much