However, this does not mean human mistakes are impossible.
Paranoid as I am of everything, I never store a seed without checking at LEAST three to five times whether I wrote down the correct words. Yet, there was one instance where I mistyped a word into another that also worked and it took me a pretty long time before I finally luckily found out where the problem was.
Checking three to five times when you are writing down your wallet seed words is good but not enough. After checking it carefully like this, and I agree that three to five times of checking is very careful practice, you will need to use that backup for wallet recovery.
It's your last checking time, to verify validity of your wallet backup. If this last checking round gives you a same wallet as your initital wallet, it shows you that your backups are valid and usable for wallet recovery.
You can end here, sleep well and don't worry that in future if you need to recover your wallet, you will end with a wrong wallet by an invalid backup.