I buy raw goat's milk and boil it for one minute and then I freeze it and it has kept for months and with no difference. I do not make kefir but I do use yogurt cheese (labane) in the Budwig plan. Budwig calls for cottage cheese which is not the same as american cottage cheese. Her cottage cheese was yogurt drained of all the whey. Here is a link on how to drain yogurt.
You can read many of my articles on budwig at the flax seed forum or you can get more info on the forum I run which is Sara's soup kitchen. Also everyday I take the Kousimine-Budwig detox breakfast and I attribute that to the healing of many.