You may not be vested in a pension if you lave too early, or you may have to accept a lower payout. This depends on how many years you worked for your employer, and other factors which are described in your pension plan document.

In some cases, the employer can specify a minimum number of years you have to work for the company in order to receive a Pension. Otherwise, the amount you receive will be vested in portions over a few years, until you will be able to leave your job and keep 100% of the accrued Pension benefits.

Generally speaking, the longer you work for the company, the larger the amount your monthly payments will be. The plan could stipulate, though, that if you leave early it may mean your pension payout is slightly less.

The same goes for the date you start taking pension payments. If you want to take them earlier than they designate, your payment will probably be less than it would otherwise be, much the same as social security payments before retirement age.

Can I Take a Periodic Distribution from my Pension Plan?
How are Pension Benefits Computed?