figure from the time you submit the amendment until the time it is processed is 9-12 months. The IRS is woefully backlogged.
here is what the IRS website states:
Status of Processing Form 1040-X, Amended Individual Tax Return: As of August 6, 2022, we had 2.1 million unprocessed Forms 1040-X. We are processing these returns in the order received and are working hard to get through the inventory. The current timeframe can be more than 20 weeks instead of up to 16. Please don't file a second tax return or contact the IRS about the status of your amended return. Taxpayers should continue to check Where's My Amended Return? for the most up to date processing status available.