My dog's at that age too. I have a friend she's usually absolutely thrilled to see- we were freaked when this friend came over and she didn't get up, even after we were calling her for a few minutes. I finally went over and touched her gently. She started, then lay back down, with this little sigh as we gave her a tummy rub that said oh so clearly- "Oh, I knew you were there, I'm just too comfy to move. You'll have to come to me."

Poor old pets!