How long would it take to crack AES-128 knowing a 12 character length password?
The average 12 character password will take 6 billion years to brute-force at 100,000 passwords per second.

WolframAlpha &quot;password of 12 characters&quot;

Allowing special characters brings this to around 150 billion years.

WolframAlpha &quot;password of 12 characters&quot; with password rules

For more information, see Security.SE:

How long would it take to brute force an AES-128 protected pdf knowing the key is 20 letter long and that the charset is A-Z,0-9?