I'm not sure how long ago workin4me saw companies with 15 year vesting schedules, but ERISA has governed vesting schedules quite a while back. From the
Dept. of Labor: "Beginning in 2002, there are two basic vesting schedules. Under the three-year schedule, workers are 100% vested after three years of service under the plan. The six-year graduated schedule allows workers to become 20% vested after two years and to vest at a rate of 20% each year thereafter until they are 100% vested after six years of service. Plans may have faster vesting schedules."
Pre-2002, there was a similar vesting schedule requirement, over slightly longer periods (ie in the employer's favor).
This are the bare minimum vesting schedules that employers can have. They can always relax the schedules and vest immediately or more rapidly than ERISA requires.
(note: I'm not a financial advisor or attorney, so I know nothing about any of this and I might be wrong.)