Should I negotiate my severance? after 12 years as an accounts payable clerk

I was offered 12 weeks of severance after 12 years as an accounts payable clerk, and I have a few days to sign. I would rather hear the honest version than the polite one. 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.

Thanks for writing this out. I went through something close to it 3 months ago, and it settled down once I kept a simple log of every call and form.