It would probably be fine to move it into its permanent tank. I generally only upgrade once for any species of snake and never had issues doing it. What size tank are you planning on moving it into? A 4x2 is generally ok for a carpet python but I would recommend a 5x2 for a coastal. My coastal is in a 5x2. I also have my jungle in a 4x2. The 4x2 works for the jungle but I plan in building it a bigger tank in about 2 months. I like them to have the extra room more for easier clean up really. I keep 2 hides in my tanks for them and proper sized ones take up a bunch of the floor space so my jungle ends up dumping on the hides a lot. My coastal has that little extra room so it doesn't really happen in its tank that often. I also wanna build a taller tank for my jungle too. Coastals don't really climb at all once full grown so you don't need height in the tank I you don't want it.
Both of them are in sliding glass tanks. If find that works good for feeding and putting back in the tank when holding as half is blocked off so less chance of them trying to climb back out. And for feeding I just open the side they aren't on so they will have to move sideways to strike at the rat instead of out of the tank.