I am sometimes worry about my Dalhouise, he wants to go out for a walk - this is a good thing because it causes me to get my butt off the chair and out the door. In the past the walk were about 40 minutes if I walked the area behind the trailer park homes circling the pond or 20 minutes if I just took him to the park down the street from the condo. However these days walks are longer and longer. Even today when I thought I would take it easy I was out 90 minutes - I would had stayed out more but he was really struggling. I think I need to get a baby carriage for him. There are so many trails and paths to walk in Squamish not to mention the side streets I can explore - and so far the rain has been holding off somewhat giving me a opportunity to get out. Every now and then I get told in person or on face book " I seen you by ..... when you were walking Dalhouise". I don't know about you - but this always makes me happy - I do want to be noticed when I am out and about.
He needs to build up his stamina is all. He's used to the short walks so the longer ones are a workout too. As I recall you just had a post about how your calves were burning. He's got 4 little legs that are probably burning a little too. :)
We take our cat out and he can usually do a couple of miles before he quits. He rides up on Keith's shoulders so that is easy enough, but maybe you could get a baby sling for Dalhousie. That wouldn't take up too much space while he's walking, but would give you an easy way to carry him once it's too much.
Here's one tutorial http://travelinpets.com/how-to-make -a-dog-sling-carrier/