Just for reference:

The Mussolini government was the longest-lasting government in the history of Italy. The Cabinet administered the country from 31 October 1922 to 25 July 1943, for a total of 7,572 days, or 20 years, 8 months and 25 days.

Source

When people talk about fascism, they usually mention his most famous apprentice, but Benito is the real deal. He wrote the book. If you follow this path, you can expect find the bloodbath in a few decades. Realistically though, there’s also a safer way out when the king is too sick to continue, but that could still take too long.