Yeah, typically, 2-5 planes do that when SFO switches from landings 28s to departing 10s and landing 19s or 10s. Very rare though, like you said it MAY happen twice in a year. Once every 1-3 years, sustained winds have planes land on the 1s for a few hours. Even then, it is usually sometime in December-March and lasts 1-3 hours in the morning. A handful of times in my lifetime, though, the winds have been so bad that the circle-to-land 1R has been done all day long well into the middle of the night as late arrivals from 3+ hour GDP delays pour in. The problem is with all the foreign carriers post-Asiana and the fact SFO tower is constantly training/washing out, these days SFO will opt to have people land in 40kt x-winds rather than put that workload on the "green" tower controllers and foreign pilots. One time I saw EVA go around 3 times trying to get down on 01R...you could tell it has been a LONG time since anyone in that cockpit did a downwind/base/final, let me just put it that way. To be fair, the mainline American/United/Delta guys often gripe about it and complain to ATC about how close they have to get to the hills and that they can't do the approach without terrain warnings...the regional guys are more like "HELL YEAH!" as they check-in with tower. Either way, it was a good show, and I really hope I get to do it at some point in my lifetime.