I've made yogurt several times now, and I still trying to figure out the most efficient way to get the best yogurt. Although I started with the crockpot method, lately I've been following Kitchen Stewardship's instructions. My first few attempts at yogurt I used store bought plain yogurt as the culture, but now I'm experimenting with the awesome yogurt cultures I got for Christmas. Yogurt naturally comes in different flavors...who knew?
On my first attempt using the cultures, I divided one packet between 2 mason jars of milk. (Per the directions, I should have added a packet to each jar.) I let it incubate for probably 4 or 5 hours. The flavor was fantastic -- sweeter and not as tart as regular plain yogurt. However, the consistency was almost that of a drinkable yogurt. I ended up straining most of it through cheesecloth.
This time, I divided 3/4 gallon of creamline milk between 3 mason jars. After heating the milk to 185 degrees and then allowing it to cool on the counter to 112 degrees, I evenly divided two packets of cultures between the 3 jars (~1/4 tsp each). I let the yogurt incubate in a cooler for about 14 hours, adding more boiling water after 5 hours (before I went to bed). I'm pretty pleased with the results. I wish the yogurt was a smidge thicker, but that's nothing that a bit of cheesecloth can't fix.