I have had a few probs with this aswell.
My way of doing it is, if doing ircuits, i switch them on as soon as the engine is on and dont switch them off untill i have dont my after landings, if im not doing circuits, i switch them on when entering the active, and turn them off when i reach cruising alt. When comming in i turn them on as soon as i start the descent to the feild and dont turn em off till i do me after landings.
Whilst i was in barbados, my instructor and i were doing some low level stuff and used irregular flashings off them to make a low level helicopter see us, and he did, but only cos of me landing lights. The problem is my instructor at home tends to say switch them off, my veiw is id rather spend a little on bulbs than not be seen, i was once told to turn my nav lights off too! And theres me thinking (after doing air law) that nav lights are a legal requirment, i must be wrong!
Rusty