If I were you, I would sit down with a piece of paper with a line drawn down the middle. On one side write "severance" and on the other "retirement." What does severance offer you? What does retirement offer you? Normally, a severance, unless negotiated, will not offer the payment of health benefits, whereas a retirement might carry some health benefits forward. A retirement doesn't mean you have to stop working, just are eligible to collect your benefits.
Personally, the way things are going, I'd start collecting my retirement as soon as possible. There will always be part-time jobs available to supplement. The only real concern is health insurance.
You might, however, be able to take advantage of both the retirement and severance. This is something you will have to check into with your human resources department. On the other hand, depending on your age, you could go to social security or your State's department of aging and ask them what their opinion would be.
Check out everything and don't get too greedy because as the saying goes, "Pigs get slaughtered."