I know there's never a 100% guarantee that you don't get an equipment swap, but in practice how often do equipment swaps between the 757-200 and 777-200 happen on LAX-EWR? I'm looking at economy on a flight (UA 1637 in a couple of weeks in case it helps here to know the exact flight) which is listed as being on a 757, which I'd be okay with doing in economy, but I'm still traumatized from my last experience in the 10-abreast economy on the 777.