Strained homemade milk kefir can last 2 weeks or longer when stored in the fridge.
While still perfectly fine to consume, with time passed homemade milk kefir taste gradually develops sourness. You may notice taste differences between fresh kefir and stored after 3 – 5 days.
When it tastes bitter, you know that kefir probably went bad. It can happen after about a week or 10 days depending on storage conditions, temperature, and how well is sealed container.
But I am sure your homemade kefir won’t sit that long in the fridge 🙂