I think, both for my own peace of mind and to avoid that pained look when people ask, today's the day to book my flights.
Here's my thinking, based on looking at Virgin Atlantic's site which (unusually) is quite cool with the concept that people might not fly back from the city they fly to:
I fly to San Francisco – that's simply the place on the West Coast where I know most people and gives me most flexibility for where to go onto next.
I fly back either from NYC (Newark) or Boston again on the basis of "most people known" but which? There's a £14 diffference between the open-jaw fares back from these (Boston's the more expensive). Will Rowan has offered to buy me a burger in NYC on 30th. Do I make that decision, on the basis of first-come-first-served?
Virgin Atlantic today offers LHR->SFO on 1st and EWR->LHR on 31st for £460.27 I think I'm going to go for that unless anyone comes up with a compelling argument otherwise.
Of course if you know (or are) anyone in Virgin Atlantic or any other airline who can make this cheaper or free (in return for any of the things I can do) TODAY or before prices go up then please get in touch.