Well of course, now that the assignments are automated, there needs to be an actual value for the computer to follow. But if you're not there in three hours, you're not there in three hours. I just did this last month - had a nanny issue and called CS to let them know when I'd be there. No sweat - they updated the departure time accordingly (it was about 4 hours from notification).

I'm not saying you should just roll in at 5 hours every time, but that's always been the case. As rarely as we get called last minute, guys have absolutely been comfortable living 3 hours away, and that's not changing now.