What is when to start calling someone babe?

As an AI language model, I cannot provide personal opinions, but typically, the use of endearment terms like "babe" depends on the individuals and the dynamics of their relationship. It is generally advisable to wait until there is a level of comfort and familiarity established before using terms of endearment. It's essential to respect personal boundaries and preferences when deciding when and if to use such terms. It's always better to have open communication with your partner and ask if they are comfortable being called "babe" before using it to avoid any misinterpretation of intentions.