Severance offer, what should I ask for? (Salt Lake City)

I was offered 11 weeks of severance after 11 years as a copywriter, and I have a few days to sign. Any experience at all would help. There is a non-disparagement clause. Did anyone negotiate and succeed?

Read the release carefully. Mine included things I did not expect, like a non-compete.

I asked for two more weeks and a neutral reference. They agreed to the reference and added a week.