We are all headed in the same direct; and that is towards getting older and as it happens it is a daily occurance. All creatures on this earth are headed the same way; I don't know of any that go in the opposite direction. It is a sad fact that our dogs do not live nearly as long as we would like; can you imagine having a dog your entire life? Well; in actuality we cannot enjoy our dogs covering our lifespan.
Without accidents or illness dogs typically live between 10-15 years of age. Smaller dogs normally live longer than the big guys; unless disease steps in. There have been several studies done on canine longevity although the stats are difficult to find. I did come up with a few sites I'd like to share with you on the subject which are listed below.
Dr. Kelly M. Cassidy 2007
Wikipedia; Aging in dogs
I have been hearing that many dogs are living longer now. Is it because of great strides in the medical field; better nutrition or simply more importance being put on the family dog? Good question. I don't know how many times I've heard people say; "we had a dog when I was a kid that was almost 20." And in the same discussion they will have told me that their dog ate what was left from the dinner table. I think the fact that more emphasis is being put on the health of our dogs and more guardians are learning and caring about what goes into their dog. And that covers food and medications; we are learning, slowly but surely we are learning. ;)