From bouncing baby pup to elderly matriarch, your dog will express different needs--and tender a range of rewards--at each stage of her life. Puppies are demanding and energetic, adolescents unpredictable. Adult dogs are eager and self-assured, and by the time they're seniors, they will have slowed to a comfortably lazy pace.

As with human relationships, ups and downs are guaranteed throughout your years together, but knowing what to expect will keep you one step ahead of the pack. During your dog's life, she will:

• Upset you--or, at the very least, frustrate you. Housetraining is no picnic, nor is cleaning up vomit or finding your slippers chewed beyond recognition. Even if your puppy never misbehaves (ha!), her never-ending need for you will sometimes feel overwhelming.
• Surprise you. Your Australian Shepherd loves agility training. Your Doberman can bark her name. Or your Cocker Spaniel actually draws a smile from the grumpy neighbor across the street. Sometimes, you'll just be astonished by your adolescent dog's endless desire to please you.
• Bring you incredible joy. She doesn't care whether you made your sales goals or how good you look for your high school reunion. Your dog is thrilled simply to be around you--and she'll demonstrate those feelings on a regular basis.
• And probably grief. No matter how long she lives, saying goodbye to a treasured friend is difficult. If it weren't, the relationship wouldn't be worth it.