Well... I didn't even START taping until 10 months old. It was on a wing and a prayer. Didn't think it would work as my guy has weak ears to boot.
Low and behold they went up. He has a little weak spot in the side because I really really suck at taping and didn't have that area properly supported. Had I been more skilled I have no doubt they would have come out perfect.
I did heavy diet supplementing too. Lots of knox gelatin. Lots of raw chicken feet. For the collagen. I even made my own "ears up" treats in the dehydrator with liver, kale, papaya, orange, cottage cheese and more gelatin as vitamins A, C and D are important for cartilage production and repair.
I wouldn't give up till closer to a year.