After making yogurt a hundred times, and reading a lot about it, I finally realized there are two types. The mild sort (incubated maybe 12 hours) is good by itself, with fruit or nuts for texture and flavor. The strong sort (incubated maybe 24 hours) is a good condiment. Mild yogurt is a poor condiment, strong yogurt is poor by itself.
My containers of yogurt spends about 3 hours in the water bath; which is close to 130F to begin. So: 14 cups of milk in double boiler to 190F, water bath to drop to 130F, add about a cup of cold yogurt to the hot milk, mix, pour into containers, into the 130F bath. 3 hrs later into the fridge. I guess you could say it’s mild; my family says they like that. The bath often is as low a 110 when I start. I use a picnic cooler for the hot water bath.