Agree it's very useful to let them see what's ahead, but with some primitives I have found that the giddy teenagers can be a nuisance, sometimes a dangerous nuisance, if running with the others at the point of birth. So now I don't put the maidens with the ewes before lambing, but add them (with lots of space and good grass, and only a few at a time) to a group of ewes-with-lambs while the lambs are still very wee. It seems to work just as well in terms of "briefing" them, but eliminates the risk of catastrophic excitement at the point of birth.