My 2 to 3 (I lose track) year old female cat has been doing this for as long as I can remember. She is ALWAYS stretching her hind legs. She is beautiful and energetic, affectionate, and eats well. Possibly unrelated, but worth noting, is she SEEMS to have poor eyesight since birth. She used to try to walk through glass doors, would accidentally walk off the side of our porch, and is always easily spooked by anyone she sees at a distance if she doesn't know who it is when they haven't spoken to her yet. Also, she's well earned her name 'Verbal', as she talks a LOT, which I assume is because she relies on sounds more than sights. Now back to the stretching... I have lots of experience with cats, so I can safely say that her stretching is definitely unusually excessive. She will stretch her hind legs before laying down, after getting up, she will even stop mid-walk to stretch her hind legs, especially if she is descending the stairs or just finished descending the stairs. I counted once, and after getting down the stairs, she stretched her hind legs 5 different times in approximately 30 seconds. Otherwise she seems perfectly healthy and happy. So why all the stretching of the hind legs?