never a problem...
I've been wearing the same pair of these since I started riding in 2000 and I've never had a single problem with them. They have fogged on my maybe 3 times since then and that was in the absolute worst conditions (there were very few of us on the mountain it was that bad). They aren't bulky at all, super comfy (and I've tried on so many goggles over the past 10 years just trying to see if anyone comes close, none do) great venting, and durable (10 years is a pretty good run for a set of goggles i think).
Bottom line is these are awesome!