Would you sign an employment contract?

all these lay offs have me thinking about the pros and cons of signing a contract with an employer.

Pros:

• you cant get laid off, and if they do get rid of you, they ether need to pay out your contract (massive severance) or your employer would need to present a "trade" to a new company.
• There is more incentive for the company to invest in you since they have you for a specific amount of time.
• You have incentive to keep your head down and not focus on other opportunities
• It could help you play more of a long game. instead of only focusing on decisions that effect the next 12 months

Cons:

• it limits your ability to take advantage of other opportunities that come up
• If massive change happens you just gotta stick it out
• Companies could fuck with comp since they know you cant leave.

SO THE QUESTION IS:

what is the longest contract you would sign with your current company at your current comp?

EDIT: what unique stipulation would you make sure you put into your contact?