Spin and Aerobic Classes on Epic

[Huddler]

We sailed on the Celebrity Eclipse over Christmas and I signed up for one spin class immediately after boarding. I planned to sign up for more once I saw if I enjoyed the class. The classes for spin and aerobics were all sold out by the first night. And the waiting list to join in the event someone didnt show up was a mile long. Do the spin and aerobic classes sell out quickly on Epic? Do I need to run up to the weight room as soon as I board and sign up right then for everything I want to do for the entire week? How are the classes and the instructors on Epic? How much do they cost? Thanks in advance for any information!