yeah, I do. We had a great dog when we first got married. He had the sweetest personality and just lived to please people. He had a hard end of his life (probably brain tumor) and was old and rickety for a long time. He was really so sweet when he was younger, though, and just wanted to make you happy.
When he was about 8 we got our second dog, who is now a pig in dog clothing. All he wants to do is find something to eat. He's very interested in you if you've got food in your hands, otherwise he's pretty indifferent. He's very demanding, barking to go out at 3 in the morning, barking at you to put food in his bowl and barking in general just because.
A few years ago when he was about 10 we got another dog. She is as crazy as the day is long. She jumps like a kangaroo and can get her head and shoulders above our 6 ft privacy fence that we had to have put in just to keep her in the yard. She jumps on people (I know, I know we try and try to train her not to, but she's got springs in her thighs and a short term memory problem). She jumps on our now 13 yr old pog-dog and tries to make him play. She runs 5 miles with DH every day and that only gives her more energy. She's our spirited child. She's just more, more, more.
I think after she passes on we're going to need to take a break. If all dogs could be like our first one I'd be all over another one, but our current canine companions are on the borderline of being more trouble than they're worth. Dealing with them when going out of town is big hassle. It's not like just anybody can take care of the high jump champ. We used to take our first dog and the pig-dog to MILs, but MIL can't deal with the crazy dog and I can't blame her.