It should be faily updated if you go on the website redbox.com and search up the location by your house and then try to do online rental/reserve. Itll show which titles each machine will have and not have. Im not sure how fast it refreshes, but there is an online inventory for each location on the web.
You can reserve online for $1, and just go to location u reserved at just swipe the card, and itll vend it, so you dont need to stand there and browse for it. Only thing is if you dont pick up the movie you still pay 1 dollar for it. IF you do pick it up that 1 dollar web rental is your 1st night charge.