I'm not sure about ages and guidelines, but both of mine are young and we try to limit the stairs. We have lots of stairs in our house, and it seems I am always running up and down for one thing or another! And, of course, the dogs want to follow me. During the day I keep a baby gate at the bottom of the stairs to prevent them from running up and down too much. It's kind of a pain, but then I always know that they're not causing trouble on the second floor and that it saves their little joints just a little. The things we do for these dogs...
Bridget, Summer, and Duke
Bridget, Summer, and Duke