I was also told that the upper 1/3 of the "leather" should be kept trimmed to avoid the long heavy hair pulling the ears down. According to the information that I found at the link below, the ears are firmly "set" by 6 months of age. I have also read other information about taping them up. We never had a problem with Toto's so I can't speak from any experience. I can tell you that she wouldn't put up with tape on her ears for two seconds! Toto was 16 weeks when we got her and they were standing up [I can't swear to it but I believe the breeder told us that they had just come up]. If they aren't going to stand [and perhaps it's too early to worry?] I would just love her, floppy ear and all!! I had an AKC collie when I was a child and one of his ears was late to stand ... I have pictures of him and it was sooo cute ... it later perked up just like the other! Good luck!
http://www.ehow.com/how_17993_care-y...e-terrier.html