Have only used them in Mk3 collars myself. I always replace the batteries well before they fail (after 15 to 20 outing) so can't say how long they last.
Mole trapper why don't you pm me your address and I will put 10 in the post. Then after you have used them update this thread and if they are any good pay up, if they are crap then don't pay. Does that sound fair?
I completely understand where you are coming from, having had cheap rubbish myself that doesn't even last a whole day.