Walk her on leash, or let her run and play? If it's the former, then yes, you should keep it to a minimum. Just enough for learning to walk on leash purposes, really. Leash walking comes into a category known as "forced exercise". That doesn't have to mean you dragging an unwilling animal along! It just means that the pace and continuity is set by you or by the dog forcing itself to try to keep up with or even to outpace you. And the problem that can arise is damage to joints and growth plates from continuous pounding.
When the pup is off leash, conversely, she'll run and play and pause. She'll naturally take lots of little breaks and micropauses that give her joints a break. That even applies largely to off-leash walks (well, maybe not for babies, but certainly for slightly older pups) where they'll bounce off ahead of you, then pause for you to catch up before bouncing off again. But they still take all the little breaks needed to avoid continuous stress on the joints.
And so, you can pretty much let your pup run and play offleash to her heart's content. For on-leash stuff though, a good rule of thumb is about 5 minutes for every month of age over 1. So a 2 month old pup is good for 5 minutes, 10 minutes for a 3 month old, and so on. That doesn't actually mean that it's impossible to take your pup further than you can get in the allotted time - you can always pick them up and carry them for a bit
