Originally Posted by
let_BAegones_be
The people who work in the lounge will have their families, friends and other plans waiting for them when they finish at 19:15, and because your flight is delayed, it unlikely that they will want to stay and work extra so you can stay in the lounge longer.
which is likely also true for the staff that work at the gate and they cannot just go home an hour before the flight leaves.
I suspect that, if the flight is delayed 1 hour and it is a BA lounge, it is likely the lounge will remain open a little longer.
Others with more recent experience of delays at sfo will be able to give an answer based on what happened when their flights were delayed