Chilling the growler is good, I've done it with ambient temp growlers to0 though, so it works either way. When you fill it, fill it as full as you can, let the foam come over the top and bring the liquid level way up. Cap the growler on foam, less exposure to oxy that way.
Growlers will stay carb'd for at least a week if the lids are in real good shape and put on tight. However... as soon as you open the growler it'll start losing it's carb pretty quick, you'll need to drink it within a couple days for sure at that point.
I've never made a point of sanitizing my growlers, as long as they are clean and odor free I feel fine about filling mine. Heck that's how they fill em at the microbrewery! : )