As I said in my thread stated Updating defense is pointless for defensing.
So you can upgrade walls to remove extra gold of your base to avoid attacker steal too much from your base. But other than that. no
If you are not attacked by the same level TH, you will be attacked by higher level TH troops. no mercy in this game.
I haven't test it. But upgrade walls will make you worst as no more attack from the same level TH, only higher one.



