Controlling variables in homemade yogurt Making yogurt at home is a fairly straight-forward process.  Heat milk to 180F (82C), cool that milk to at least 110F (43C), add live cultures, usually in the form of yogurt with said cultures, incubate, then chill. 

There are several variables in the process, some of which are: The fat content of the milk (I typically use whole), how long to hold the milk during the initial heat step, how long it takes to cool the milk, the temperature of the incubation step, and the length of time for incubation, to name a few.

While length of time for incubation, and temperature at this stage, clearly contribute to sourness, I am trying to nail down the variable that contributes to a creamy texture.  I'm not referring to breaking or clumping, as described in Why isn't my homemade yogurt smooth?.  My yogurt comes out smooth.  

My initial hypothesis is that holding the milk for a length of time at the initial 180F(82C) (rather than immediately removing from heat and/or chilling) has an impact on final texture. Any thoughts or experience that might inform my hypothesis?
The initial heating stage takes a little time to denature the water soluble proteins in the milk.

The hotter your milk, the faster the process. At 180 it takes 30 minutes. At 190 it takes 15 or so. Heating the milk longer than this won't improve the texture. I don't believe the texture will change very much unless too much water is lost.

Heating for a shorter time than this will make the yogurt significantly more fragile and less creamy.

"The milk mixture is pasteurized at 185°F (85°C) for 30 minutes or at 203°F (95°C) for 10 minutes."
http://www.milkfacts.info/Milk%20Processing/Yogurt%20Production.htm