What age can is safe to start running with my V?

Captain is just over 8 months old and we've run with him a few times- all under 3 miles, but on pavement- starting at maybe 6 or 7 months- but is it too young to start? I was trying to be conservative and just do a couple 2-3 mile runs a couple times a week, but I don't want to put him at risk for bone & joint problems later. So when is it officially safe to run with them? And I assume, no matter what, they shouldn't be running on concrete all that often no matter what the age, right?