In my previous life we relied heavily on rear crew to tell us what was going on. In two cases the info they gave enabled the flight deck to make the decisions required to save all their lives. Nimrod with bomb bay fire at St Mawgan when they turned back to land on reciprical and Nimrod ditching in the Moray Firth after an uncontained fire started by an errant air valve/starter motor. In both cases it was later assessed that the aircraft had been very close to structural failure within minutes. Tragicaly in Afganistan the crew were unable to get on the ground before that structural failure occurred.
I accept that pod mounted engines are different as they should fall off but it does illustrate how deadly an uncontained airborne fire can be and how little time may be available to you. For all you know the fire may be due a fuel leak ala Concorde which will rapidly spread so best to stop in my view. Would I stop at V1/rotate on a long non FLL runway with 7000' left ?, in the sim no, in the aircraft with a fire warning then yes I would and take my bollocking.
As an aside I always make a point in the sim of getting the senior cabin crew to do a visual on any engine that indicates the fire has been extinguished as fire wires have been known to burn through and thus indicate all is well (ish) and previous indicates that info from the rear may well be crucial.