Could never understand the fuss about a game's length. I really hate when people impose these 'unofficial requirement' on each game, regardless of genre or content. A lot of developers have folded to this perception, and it has a negatively impacted their games. You sense the team lost focus, with the game feeling unnecessarily bloated and uninspired, with a definite lack of polish as you progress further and further.
A Lengthy design just doesn't suit every game. Certain types of games are way better off focusing on a densely packed experience with high replay value. Star Fox is considerable shorter than any Zelda game, but it's not a game I'd play just one or two time through. Conversely, I don't have the desire to play a Zelda game multiple times, nor would I impose a "high replay value" rule on such a game. So why impose a "X-hours length" requirement on games with potentially high replay value?
Of course, you can always do like Kamiya says, and just not buy the game. As for me, if it's as good as it looks to be, whether it's 4 hrs with decent replay value, or 40 hrs with very little, I'll buy it at a high price!