Severance offer, what should I ask for? - 17 weeks in

I was offered 11 weeks of severance after 11 years as a web developer, and I have a few days to sign. Any experience at all would help. It includes health coverage for a couple of months.

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.