Well from what i've gathered talking to people on the GTP boards, Biaks take the longest to change colors, some actually change their whole lives. The other subspecies change color very quicker seeming almost like overnight. So I'm expecting Pat to hold yellow for a very long time. I saw some Biaks thats were 3 years old and still had a lot of yellow on them. The one thing about GTPs is they seem to be very variable in colors and you really never know what you will get until the snake is an adult and even then, it can still keep changing.
So basically i got Louie and Pat to look forward to see changing colors as the years go on.