Hello, I'm new to the forum, and I hope it's okay if I just jump right in with a question concerning my eight and a half year old husky/yellow lab mix.
My boy, Taz, and I have been running partners for three years or so, and this year I'm considering training for a marathon or half marathon. He will be turning nine in May, so I guess he's getting on into his golden years. He still seems to hold his own just fine on our short runs, but last night I took him tobogganing (

)and for the first time, he wore out before me. I noticed last summer, too, that when he would run beside my bike, he was a bit slower than he used to be - I've never been able to outpace him on a straightaway before, and I know
I'm not getting any faster lol. So he's still in really good shape, but I'm seeing signs that he's past his prime.
I'm wondering if the training would be too much for him? I think training for a half marathon would peak at about 25 miles per week. Now, obviously we wouldn't run in warm weather, I would watch him for signs of fatigue, bring water along, etc., but what I'm really concerned about is if it would be too much stress on his bones and joints. I have read that giant breeds don't make great jogging companions for that reason, and I'm wondering if the same holds true for older dogs?
I really don't think I would bother if he can't do the training with me, because it would break his heart to see me go running alone. It's his favourite thing to do in the world, and if I try to go alone (I left him at home a few times last summer, because it was too warm) he cries the whole time I'm gone.
Typing this out, I'm kind of getting the feeling that I already know the answer (that it would be better to stick to shorter distances), but I'd love to hear other viewpoints. After all, at least 50% of him is bred for endurance running, and I know that he'd just love it. I just don't want to inadvertently do any harm to him.