RB,
Fair enough if you get it just right every time, but you are expecting your less experienced FO to be as good as you, whilst letting him know he'll get what-for if he doesn't measure up.
One go-around because he gets it wrong negates all the fuel savings you desire for a couple of years. One "Press-on" hot/high approach is potentially much worse!!
Given the choice between going for the ragged edge of efficiency or being a little conservative, I'll "Waist" the 15kg of fuel to ensure a safe outcome.