Despite the fact I've had a number of backpacks throughout the year, none have ever really broke. Inside might get ripped or something,but I usually kept mine in good condition.
Though the part to hate about getting a new bag, the zippers/compartments might be diff. Use to putting specific things in specific areas in the bag, and once you get a new one, things are in diff locations and you have to put all your stuff in new places within your bag/forget half the time where certain things are.