You can wait for quite a while... if you're wanting to get those pups going as individual plants, maybe until they are about the same width as the mother plant. You can certainly start them smaller than that, but you will benefit from letting their connection with the mother plant allow them to grow bigger and stronger before you remove them. There is always a sort of tradeoff between time and size when it comes to removing offsets. Tiffany has asked some really good questions which may help guide the decision. You may also wish to decide (depending on your climate) whether you will put the plant outside in the ground at some point.
Another thing to consider is the sprawling behavior of the mother plant. Your plant is one of the aloes which tends to grow up for a while and then sideways when it gets top-heavy and the stem is longer. That is mostly normal for your plant, though it can be reduced or delayed somewhat with very strong light. At some point in the near future you may have to stake or tie it in order to keep it from falling over, or tipping the pot. Just as fair warning. At that time you may wish to consider pruning the mother plant and letting the babies grow up to fill in around her, which can help provide stability (for a while).
