There are some essential elements to consider when making kefir;
Temperature: Room temperature is great for milk kefir. We have found that anything in the 18-25°C (64-78°F) range will work just fine. In our experience, a broad range of “room” temperatures work well for kefir, but major changes in temperature will impact the speed at which your kefir ferments.
When the seasons change, your kefir will most likely need a little adjustment time. Warmer temperatures will speed up fermentation, lower temperatures will slow it. We find that in periods of seasonal change, kefir is sometimes thin in consistency or very yeasty smelling.
Don't let this bother you too much, as they always come out fine after a week or two of adjustment.
Keep your fermenting kefir away from direct sunlight.
Aerobic or Anaerobic: There are different kinds of fermentation. Some require air, others require no air. Milk kefir is technically an anaerobic process, but you don’t need to work to keep your grains submerged like you do when pickling vegetables.
Fermentation Time: There is definitely some subjectivity here, although you do want to care for your culture by giving them a somewhat balanced living environment. The longer they ferment the more acidic your kefir will be and the lower it will be in lactose. We don’t recommend fermenting for longer than 48 hours. Although these culture strains are acid tolerant, even they have their limits.
Our preferred time is 24 hours during stable periods. When the weather gets very cold, they usually need at least 36 hours. When the weather gets very hot, they are occasionally done in 12 hours.
Sugar: The cultures need the sugar to thrive and grow off. Without it, the culture won't activate - sugars can be found in milk (lactose), coconut milk & water & fruit juice etc.
See the How to Video for Kefir so see what it should look like when it is set.
Note - if you leave it longer it may separate, this is normal and you don't need to worry, simply shake it up before storing/consuming.