You can make crab and shrimp enchiladas up to a day ahead of time, and refrigerate them until you are ready to bake them. To bake, remove the prepared enchiladas from the fridge about an hour before you want to put them in the oven. Cover with foil, and bake at 350°F | 177°C for an hour, uncovering them for the last 20 minutes of baking. The internal temperature of the finished casserole should be at least 145°F | 63°C.