Severance agreement arrived, need a second opinion - 8 months and counting

I was offered 13 weeks of severance after 13 years as a pharmacy technician, and I have a few days to sign. I do not want to leave money on the table. Did anyone negotiate and succeed?

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

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