Tweetpermanent thyroid shutdown is a myth (widely held one, but still a myth). 25+ mcgs is generally believed to cause a temporary natural shutdown.
It's longer than most recommend, but you should be ok if you run a slow taper: 25mcg, 12.5mcg, 6.25mcg for a 10-14 days each for the 4th month. You could even keep the 1/2 or 1/4 tabs going longer as those doses don't shut you down. It could take 6 weeks to fully recover, so low supplementation during that time may help since you're running it for an extended amount of time.