I think what marekk means is : is there a regulation for a period of time for the actuator in which it must reach it's normal position, or the teams can play with that. Normally you want it to go to low DF position ad fast as it can, to maximise low DF advantage, but what's the case with other way ?
EDIT : I don't think delaying the high DF position would do any advantage. Normally if you hit the brakes at the end of the straight, you want all the DF to be avaliable to help breaking...