I've read that American bloodline and German bloodline GSD's can take different lengths of time for the ears to stand up completely. What I've read says weeks to months.
Well, my German GSD's right ear perked up early on. He is now almost 7 years old and his other ear just started to stand up by itself. At first, it would only stand up after he'd been outside in the cold for awhile, then when he came inside and warmed up, the ear would go "friendly" again. Over the last couple of months, the ear has consistently stayed up, inside or out, warm or cold. It is still not quite a rigid as the other one, but it seems to be getting stronger and stronger.
I've never found it important for his ears to stand up, so glueing/taping/whatever was never even a thought. While it does make him look more intimidating with both ears erect, anyone unknown to him who would have thought he was a pushover because his ear flopped over would have been sadly mistaken had they tried to enter his yard.
So, for those who say that the ears won't stay up if they don't stay up after some number of months early on, that's not entirely true.