ive heard that smaller dogs live longer than bigger dogs.
is this true?...

It all depends on the breed, how well you take care of the dog, how well life treats the dog. For instance, one of my dog's is a dachshund, and I have heard people say that they have had Dachshunds live for sixteen years, as everything went right for the dogs. At the same time, Dachshunds are very fragile dogs, and one injury can really shorten its life.

I think it all depends on how well they were taken care of and if they didn't have any health problems. We have had labs and collies and a few mixed breed dogs that lived for close to 20 years.

Books say, yes, smaller dogs live longer, the bigger the dog the less years. But, as we all say, we are now taking care of our dogs better, than, shall we say, our parents did. That helps, so smaller dogs, on average, 12 yrs. Large dogs, 9 to 10 yrs. again, on average.

As per experience, the dogs that I have taken cared had their longest life at about 13 years. The latest dog we had was so old, he wasn't able to eat anymore and vomited everything that he puts in his stomach. It was such a hard sight for all of us considering that he was even older than our oldest son. He died last year and until now, we didn't like to have dogs anymore for fear of that happening again.