I agree with the teething thing, but the use by the body of calcium is higher while the puppy grows. Increasing calcium can be risky because excess calcium can cause calcium deposits in the joints. It may be ok if the calcium/phosphorous ratio is correct, which happens when you feed raw bones. Other forms of calcium supplementing should avoided.
But that calcium needed for growth tends to cause the ears to come down. This is why some puppies have their ears stand all the way through, and some come up after teething and some wait until they are 8 to 10 months old, sometimes older for consistent ear-carriage. I think it is all growth.
The rule of thumb is if the ears have stood prior to the growth spurts and teething, they will stand again.
My feeling is that if you are going to show the dog, or if having the ears not come up will cause you to be disappointed in your dog, then certainly have someone with experience help you with the ears.
Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.