First off, note that head does NOT equal carbonation. Your beer will have head 4-5 days after "set and forget" carbing, but not much CO2 will be actually dissolved into the beer. If the beer style calls for 2.5 atmospheres of carbonation at 11 PSI at 38 degrees (all made up numbers, the math might not be correct), then it WILL take 14 days to reach those 2.5 atmospheres of dissolved CO2 in the beer.
Second, just note that 38 degrees is a little low for a homebrew serving temp. The experts (Jackson/Palmer) say the following: Typical homebrew ale should be served around 50-55F, homebrew wheats and lagers at 45-50F, homebrew stouts and porters at 55-60F. Nothing wrong with your kegorator being set to 38, as this helps with freshness and helps CO2 dissolve, but you may want to let the brews breathe and warm before serving. If not, at 38F you are losing a ton of the hops and malt character in the brew.
Hope that helps!
Primary #1 - Midnight Ryeder (Midnight Wheat and Rye)
Primary #2 - Florida Weiss
Primary #3 - Kane-DOH APA (Honey Citra APA)
Secondary #1 - Downtown Flanders Brown (brewed August 2012)
Keg #1 - Raspberry Florida Weiss
Keg #2 - Cinnamon Raisin Cider
Keg #3 - NONE!
Bottled - NONE!