I think something around the bulk and weight factor of good ski goggles (about 150g, as compared to the Quest 3's 722g and more if you want a headstrap that's actually comfortable) would be enough for AR devices to start seeing regular professional use (mechanics, plumbers, and so on) and to start showing up as mass-market media consumption/2D-game-console-replacement devices. At that point it would be comfortable enough for non-enthusiasts to wear for a few hours at a time without complaints.