I haven't actually tracked it, but it seems like the 2to1 conversion recipe shows up every few days (four, it feels like). I have it now but still seeking the last artifact needed to craft it. Almost there, but I don't think I'm going to acquire it before the recipes change again. I'm not too concerned; I'm expecting to see it a couple/few more times before the event is over. Hopefully it is in the last rotation of the event, maybe again in the day following, for those finishing getting the last artifact at the last minute.