The answer to this question is that it really depends on your goals and what you want to accomplish. My general recom-mendation is to add a new sign once your baby has successfully started using an old sign. This means that you will have several on the go, usually around 5-10, and are then continuously adding some new ones as your baby adopts the ones you’ve already started.
You really can’t add too many signs so long as you keep signing them once you start, however, working on just a handful at a time, while continuing to sign the old signs, ensure that your baby doesn’t get confused or overwhelmed. At a certain threshold, your baby is going to turn into a sponge and take up information at a much quicker rate – the signing explosion. You might be surprised by how much more difficult it is to continue to introduce new signs and keep using the ones baby is already signing.