Took me about 15 hours in 4 days, mostly trying to rush through.  It seems like a pretty ideal game to play over a week.

Rent it?

Do it at two different stores.
 
 
Problem solved.

I don't think you should do it (that's almost like pirating :O) but yes, you could do it.  It's around 15 hours if you do very light exploring, I beat it in 18 hours with a medium amount of exploring.

yea, it goes relatively quick if you've got time to sit and play. Figure 10-15 hours, plus most achievements/trophies are right on the path without going out of your way aside from 4 or 5.