"Old dogs, like old shoes, are comfortable. They might be a bit out of shape and a little worn around the edges, but they fit well." — Bonnie Wilcox 'Old Dogs, Old Friends'

There is no reason that the same couldn't be said for cats.

Early life with our pets is an ever-changing process, and albeit joyful, it's challenging. Puppies and kittens have boundless energy, and as anyone who has shared life with a new four-legged creature knows, you have one eye and one ear on them at all times. And, just when you think you've got them figured out, they grow mentally and physically a bit more.

It's tremendous fun, but regardless of how many times you've gone through early pethood, it's always surprisingly rewarding and exhausting.There are a of of kinks to get worked out, things to help them learn and discover — until they turn into adult pets.

I've been told that having a puppy is more difficult than having a baby. As someone who doesn't have children, that surprises me, but I'll take everyone's word for it.

Life coasts for awhile; the relationship builds for years, memories are made — and then the later years, a truly magical time — begin. I think it's the time when you realize that you and your family are, unquestionably, "pet people."

Everything about owning a pet becomes crystal clear at that point; the unspoken language that exists, the comfort level; it's like any other relationship that lasts long enough.

You know each other's habits so well that you naturally, easily, "make room" for each other. As much as our companion animals are unfolded in many ways due to our nature, we are as unfolded by them, much like an old married couple.

It's refreshing to see this happen, because sadly, in our throw-away society, it's so easy (and perfectly acceptable in some circles) to part with a pet.

In this weeks' Pet Photo Friday slideshow, we compiled photos from readers who shared a glimpse into their lives with their senior pets. Some of the dogs and cats that you'll see have been with their families from young pethood, while others were adopted later in life, and others were already seniors when the connection was made.

Do you have a companion animal in your family that you want to show off? Taking part in our Pet Photo Friday feature is a snap — simply email a photo of your pet to ppsa2mi@gmail.com, any time during the week. Please include the animal's name, age, and city or township of residence in your email. Be sure that your photos are 1200 pixels wide and in .jpg format.

We'll put the photos into a slideshow series, publish and promote on Friday here in the Pets section.

Lorrie Shaw is lead pets blogger for AnnArbor.com and wrote "The bucket list for pets". Tag along with her daily pet adventures on Twitter.