A large number of factors affect what the executive is offered. These include employer size, industry, employer's economic health, employer's past practices and region of the country where the employer is located. There are a number of conventions as to how much severance is appropriate. None of them necessarily means anything.
Some executives believe they are worth at least one month of severance pay for every year worked.
On that, some executives argue that they should be paid severance that will cover them for the entire period during which they are likely to be looking for a job.