I always understood (or perhaps misunderstood) that lagering was done on the yeast and that it was the presence of the yeast cake that cleaned up the beer and gave it it's fresh, clean character. So I rack after primary fermentation has settled down and then leave it to completely clear and lager- about 6 weeks. It's at this stage that MJ's M84 Bohemian Lager yeast produces a film on the surface. Not an infection as I've had this over several different brews over a couple of years- and the beer tastes good. I don't krausen the bottles as there's always some yeast present in the perfectly clear beer. It takes a good few months for the beer to condition, though. Having said that, I brew lager in the winter for consumption in the summer.