According to Square Enix, you'll get 150 hours of play from Just Cause 2 without having to look any further than your boxed copy.
“... We’re getting reports of close to 150 hours of game in the box, that’s about 26p per hour of riotous fun. Tell me another form of entertainment that offers that sort of value?” Square's UK marketing director, Jon Brooke, said to MCV
(Picking fluff from your belly button can provide 150 hours of entertainment for free, if you've got the stamina.)
SPOnG's latest Just Cause 2
preview can be found right here