leave. Some require, not only tickets, but a timed entry.
The Eiffel Tower, Louvre, Versailles, and Ste Chapelle all fall into the timed-entry category.
Don’t plan do many things to do that you don’t have time to appreciate where you are.
Versailles is easily an all-day trip.
Stroll around the Latin Quarter, visit the Pantheon, some of the local churches, the book sellers along the bank of the Seine.
Eat at bistros that are away from the main tourists streets.
Have a great time.