My hardware warranty
I personally warranty most of my hardware for at least a year. Usually, I get a three year warranty, so it gives me a large cushion in the event a customer comes in a month after the repair is done or brings it back for repair a month after their warranty expires, or the part sits on the shelf for a few months. I've only had to warranty one hard drive in the year I've been in business and that was pretty much a breeze because I have an account with Seagate, who warranties most of their drives for three years from the time I purchase them. As far as laptop screens go, those also carry a three year warranty from the date I purchase them and so far, I've never had a warranty claim yet.
One of the biggest complaints I hear from customers is that "my computer crashed a day after the warranty expired and they won't honor it, so I'll never buy another computer from them", so I figure this is one of the few ways I can compete with good 'ol Wally World lol. I usually won't purchase anything with less than a three year warranty, unless I have to, because I know how ridiculous some people are about warranties. They expect you to warranty it, even if the warranty expired a week ago and I would rather not argue with them. A one year warrant gives me a lot of room to work with the customer in the event something like that happens.
If a customer requests used parts because of price issues (usually with laptop screens or motherboards), I let them know up front I can't guarantee or warranty the parts or my labor. Most of the time they will just go ahead with a new part because of the uncertainty.
Motherboard repairs (usually laptop chipset problems) that I have to send out for repair only carry a six month warranty on parts and labor because that is all I get from the repair facility. So far, I have had no issues here either.
Some things I pay particular attention to is the reputation of the whole-seller, the manufacturer, and the quality of work an outsourced repair shop does, when considering how long I will warranty an item for.