I was always taught "No emergency actions below 500ft unless its a double engine failure or we are on fire" on take off and "no emergency actions at all unless its a double engine failure below 1000ft on the approach". the thinking being that an accurately flown approach will get you in, and then you can sort out the mess on the ground.
A set of hands flashing around the cockpit are potentially lethal if the handling pilot is not able to give 100% to monitoring them at an already high workload and stress moment.
I had one inexperienced lad shut down the wrong engine on me in the sim through excitement and watched my boss (16,000 hours) b***er up a perfectly good ILS on an IRR when doing touch drills on a single pilot aircraft below 500 ft just as everything gets really tight.
We have a procedure here that no drills are to be carried out on approach at all, and that no emergency other than a double engine failure needs a reaction until the pilot is absolutely sure that the aircraft is at a safe height and on a safe heading and that he is aware of the surrounding terrain.
VH