My son reached 180 signs by 21 months. Is this unique? Maybe and maybe not. Most average toddlers can easily master this many signs and even more. Most won’t get past 50, but that has less to do with the student and much more to do with the teacher. Children are like sponges and they can only soak up what moisture they are exposed to.
I will say that we could have easily taught more signs because there were periods of time when we had no new signs on the go. We had moved onto talking and we just didn’t add more from the dictionary. If you have grandparents helping, babysitters or other caregivers, aunts and uncles and so forth, you can easily spread the workload out and teach many, many signs. All the while you sign, your toddler will be picking up new spoken words too. Baby signing is not meant to replace spoken language, it’s just used to patch them over as their ability to talk grows.
How much effort you put in will play a huge part in how many words your baby will sign. As I’ve mentioned several times in this blog though, baby signing is not a competition and you shouldn’t be comparing yourself and your baby to other parents and their babies. What is important is that you use baby sign language to suite your requirements. Baby signing is a way for you to connect with your developing baby much sooner than you could otherwise.