hello, i want to buy a macbook pro, it's an older model and it's on a big discount with limited stock. is there a way to know when a macbook pro was first used? i don't want to get a macbook that has been on the show room floor with the backlights on for tons of hours, i have a macbook that already had a screen replacement because of the time used up on the backlight. any app for that? or something else? thanks.