They do. I lost my pit bull last December to cancer; I had her for more than a dozen years. We didn't have it diagnosed or treated (chemo) because she had already outlived her life expectancy and I didn't want her to deal with side-effects from the treatment, but we kept her comfortable, and when that time passed we all went for one last walk, then a tearful trip to the vet. You miss those big bundles of unconditional love.