Bought a set of 5 brand new winter tires from Costco (Bridgestone Blizzak W965, not too much choice for this size). Brought a spare set of 5 wheels that were there from the 1990s with original AVON RangeMasters on them. Told them to make sure they replaced all valve stems and they said "OK".
Drove off, and, not more than 5 minutes away from Costco, while driving on a highway at 100kmh with kids in the back, got two flats (front left and rear right). Pulled over and sure enough the idiots left the old valve stems in, which were losing air like there's no tomorrow.
Towed the truck home and am going to have me a nice conversation with the Service and Store Manager today about why they decided to put my family's life in danger...