Re GS:
Back when I was still on the ER in NYC and they were giving out GS's like candy, I'd get a call that would start with, "Hi, this is xxx from scheduling. You wouldn't be near the airport, would you?" Being a commuter, the answer would always be no. They'd say "No problem," and move onto the next guy.
One time, they asked how long it would take to get to JFK. I told them if I got on the flight, about 4 hours. They held the plane and even offered to PS me if I was going to have trouble getting on (I didn't).
The point is that the schedulers (at least a couple of years ago) understand that with short notice GS's, there's a reasonable chance you can't accept.