If your adoptive pet is over five years old, your time with them will be limited. It is good to consider that there are always plenty of young adults or adolescents, who have never had a chance to experience a stable and loving home. If you select and older pet, out of pity, one of those youngsters is not going to get adopted. While age is not a huge impediment to making the perfect adoption, it may still effect your decision. If you are looking for a puppy, age is relatively unimportant.
Adult dogs are usually in a shelter because they have somehow lost their appeal.
By far, most adult dogs are surrendered to a shelter for behavioral reasons. In the most cases, the problems can be fixed with a minimal commitment of time, effort and money. Many of the dogs in a shelter are there because of unanticipated problems in the family. A child who becomes allergic to the family pet may cause a concerned parent to reluctantly find a new home for Fido. Sometimes single dog owners die and leave their heirs the task of caring for their remaining pets.