Only SLF so I have no real idea but it seems that the schedules must have a degree of fat built in so there is some scope for "putting the foot down". Last week we were on an SQ from CDG and by the time we actually took off it was an hour later than the scheduled time of departure (yes, I know that the time refers to push back not getting into the air) but we still made it into SIN ahead of the scheduled arrival time by about 15 mins.