There is no "left over" pension. Companies do not have a fixed amount set aside for your pension that will continue to pay after you both die. Instead, they figure the cost based on an average life. If you die early, someone else who lives long will be collecting. Or if you live long, you collect more. Annuities work the same way.
Normally a pension is for one person's lifetime. Some companies allow you to take a reduced pension, but it will pay your spouse after you die. There are some companies that will let you select "10 year certain" pensions that will pay your heirs for the remaining term if you both die before the end of 10 years; again, it will cost you a reduced benefit.