Would "well done" also apply to a case, in which the performer of the action, the one for which he is receiving a praise, is still performing it at the moment of receiving the praise, in other words, when he is not done yet?
Dad: "Okay, now start jumping over these obstacles and keep doing it for 5 minutes"
Son: "Okay, Dad!"
Dad (1 minute later): "Well done. You are doing really well!"
or something like that.