Here is the warranty on liftmaster openers breaks down. Openers made in the last 5-10 years that have a DC motor have a lifetime warranty on the motor itself. Also any belt drive opener will have a lifetime warranty on the belt itself. There is also a 5-year warranty on the other parts. And also if unit has a back up battery then there is a 1-year warranty on the battery.
Garage door openers manufactures have similar warranties
Pretty much all the other manufactures have similar warranties on their equipment. But if you buy an opener from a hardware store for do it yourself installation the warranty will be different so check with the manufacturer on these kinds of openers. Manufactures usually have lesser warranties on these openers because people with little or no experience could improperly install them and shorten its life. The Manufactures can tell these units from professional grade openers by the model or serial number.
You can find warranty info on any new opener from the manufacturer website. As far as Liftmaster goes I have only had to use a warranty covered part twice in 13 years. They shipped it to me in 2 days and the customer only had to pay for the labor to repair opener.