We have a staircase leading up to the 2nd floor. Remi was too scared to use them at first. Then he surprised us one day, started to climb them, and fell through the open stairs to the hardwood floor below!!! I was terrified, but he only fell from the 4th step, so it was no big deal.
Going up was easy, going down was another story for him. He still gets nervous sometimes going down foreign steps. (now 5 months)
When I was at the local pet supply store, the trainer there did mention I shouldn't let him climb the stairs due to his joints forming. Honestly, I let Remi set his own pace. I was relieved when I no longer had to carry a 20-25 pound puppy up and down a flight of stairs for every potty break.
Btw, I just have to say, Angus might be the prettiest pup I've ever laid eyes on. What a knockout!!