Pretty much what everyone else has said. If they work their performers down, they'll leave faster, and they'll have to pay heavy costs to recast. Not to mention Lin is the star cast member and surely has influence in these types of decisions - I doubt any cast is going to vote for doing a 9 show week.
If they really had the goal of maxing out on the money from this thing, they could just raise ticket prices by a significant margin. A jump in price of $25 per ticket isn't going to dissuade anyone from seeing the show at these levels of hype, and $25 * number of seats in house * number of performances before they have to lower prices to more manageable long-term levels is an absurd number.
BROADWAY: The Cripple of Inishmaan, This is Our Youth, If/Then, Hedwig and the Angry Inch (x3), Cabaret (x2), The Real Thing, A Gentleman's Guide to Love and Murder, Chicago, Les Miserables (x2) Disgraced, Finding Neverland, On the Twentieth Century, Wolf Hall Part I, On the Town, Fun Home; TOURING: Jekyll and Hyde, The Book of Mormon; LOCAL: The Twilight Zone, Anne Boleyn, Death and the Maiden, The Lying Kind, Chorus Line, Stupid F**king Bird