Should I negotiate my severance? after 5 years as a quality inspector

I was offered 5 weeks of severance after 5 years as a quality inspector, and I have a few days to sign. It has been weighing on me all week. There is a non-disparagement clause. Did anyone negotiate and succeed?

Ask for the offer in writing and do not sign on the spot. A day or two to think is normal.

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