Yes, you can! You are able to have up to 6 standing reservations at any time (4 standing reservations if you have the "Lite" membership). Once you have checked-in to a lesson you are immediately able to book another. Alternatively, you can cancel an upcoming reservation if something more appealing pops up!
You are able to view and reserve lessons 2 weeks out. You can view your upcoming reservations either through the app or the website, and can cancel them from either as well. Remember that you can visit each location 2-4 times per 30 day period depending on your membership.
Not sure where you stand on the number of visits to a certain location? You can monitor this via your Account Settings tab in the app. Past, future and missed reservations count in this number so keep that in mind!
Note: A reservation in the future also counts as one of the visits. A free fitness visit also counts as one visit.