Should I negotiate my severance? after 18 years as an accounts payable clerk

I was offered 18 weeks of severance after 18 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. I do not want to leave money on the table. What did you ask for?

An hour with an employment lawyer cost me a small fee and made me feel much safer about signing.