Depending on what the problem is, sometimes they don't give you any option except depot. That's generally when they don't have a clue what the problem is and it might be multiple parts. They generally won't do the "shotgun" approach to repair using NBD on-site warranty. Fortunately, things that go wrong are normally pretty easy to diagnose. I've only had to use a depot repair once during a 5-year warranty and I was not pleased with the outcome. It was very fast (total of 5 days including shipping) but they screwed up some things and I had to get them to send me a couple of replacement parts that got broken by their depot muppets. My preference is NBD parts-only dispatch. I don't need a tech and don't like strangers touching my stuff.