<<How much extra flying time is this adding to the SFB run? Are they having to land in Canada or anywhere else to refuel??>>
In the 757, it takes 10+ hours with a good chance of a fuel stop in Bangor, Maine. With the 767 it's sub 9 hours without needing a stop.
We did this in March but we had the 767 out and 757 back which also doesn't need an inbound stop due to favourable winds. We were 10 hours out and 8 hours back with no delays.