Water from fridge not going. Water from fridge not going down plug hole into container.How ofter

Question

Water from fridge not going down plug hole into container.How ofter should the water container be emptied at the back of the fridge/freezerI have a sub zero frigerator #550 its about 15 years old. The drain tube is freezing up and ice is building up on the bottom of the unit. it also ismaking the refrigerator smell. Can you help????