DH is doing the yorkshire three peaks challenge in July for charity. It's 25 miles in 12 hours climbing 5000 feet. He wants to take our 20 month old lab with him but I'm really concerned. I think it's far too much strain on such a young dog but Dh thinks I'm being daft and he will be fine. What do you think? I'm hoping I can either put my mind at rest or persuade dh otherwise.