a standard vesting schedules is 4 years with a one year cliff.
That means that after one year the person will have vested options worth 10% of the company. they will then accrue more options every month until they've fully vested their 40%.
That doesn't mean they'll only get 40% after 4 years.
And typically when you are terminated without cause a good vesting contract will foresee in that and trigger the 'accelerated vesting' portion of the contract. Ditto with an early sale and possibly other trigger conditions.
That doesn't mean they'll only get 40% after 4 years.