There are currently 2 types of sessions (in terms of frequency) that a mentor can offer to a mentee: one-off and recurring.

One-off sessions can be identified on the profile as it just contains the session title and duration (see Coffee Chat with Me.)

On the other hand, recurring sessions contain the title, duration, frequency, and the number of sessions in the series (see Craft Your Portfolio.)

It's important to note that not all mentors offer recurring sessions. If you find a mentor you'd like to have recurring sessions with but they are not offering it for you, it's best you to reach out to them via Messages.