Frosty Hoar
It also depends on the logic used for your flight plans. In our case the 120mins equals 840nms, however the CFP immediately drops the aircraft from cruise altitude to FL100 at the ETP, the calculation is there based upon 375KTAS, which in turn will give you a greater time than 120min even with NIL wind.
So basically the time can be exceeded but you may not operate outside your defined area of operation.
Mutt.