My Midori was 12wks when I got her from the breeder. Her ears were not standing too good on their own. The breeder showed me how to tape them and we did it together that night before I took her home. When I took the tape off, her ears were standing and have been ever since, but I do keep them trimmed and she is only 15wks right now! (the breeder said she had arleady done it once herself though)
If you do tape them be ready for lots of crazy questions from everyone and their brother when you take your puppy out in public
I guess I don't really know if it was a good age to do it, but it worked!