Sounds like it is time to re-size
I re-size my bets when I double my BR or it drops in half, so I would probably leave because I would want to do some re-calculating. Come to think of it, assuming that this was not a -6 SD event, it would take me at least 10 hours to lose 1/2 my BR, so I would probably leave because I was tired.
I generally keep my sessions to 45 minutes max for cover reasons, so I have never experienced the scenario you describe.