Coach's Official Guarantee (from the website)
Coach products are made to ensure satisfaction and service for the natural life of the product. If, during its lifetime, your item should require repair, we offer a repair service for many of our products. There is a shipping and handling charge of $20 (plus tax, where applicable) for each item submitted for repair.
The people that are able to bring in a bag and get another one for free are generally those that purchased it fairly recently with a receipt and the store has or can find a replacement readily available... Sometimes it also depends on the SA and if you have a good relationship with him/her/them. I've brought in my bag 2.5 weeks later with it's receipt due to a defect and since it was so recent they still had it on the floor and replaced it.
The exception to this is the known Carly fraying issue - for that, they will give you merch credit towards a new bag for Carly's MSRP on the spot no questions asked.
More often than not, even if you have a good relationship, it gets sent in to JAX (main warehouse) for review if they can repair it or not. If they can repair it, they will, if not, they will send merch credit for the MSRP of the bag (unless the creed is stamped, they will give credit accordingly, like a bullseye stamp means outlet, then they will give you the value it was at the outlet), or if the bag is older, they'll send the bag back unrepaired and give a 40% off one item. Some stores will waive the $20 fee sometimes, others will charge you the $20. This is what happened to my Julianne, I was a frequent customer and it was my first time sending something in, so they waived the fee.