Hiding your duration of a package is as simple as a toggle switch
Hide Your Duration
The default mode in Rex shows the duration of all of your packages.
If you don't want the "package duration" to be visible, you can hide the duration using the toggle.
Package -> Package Controls -> Hide Package Duration "on"
If the Hide Duration toggle is turned ON, your package duration will be hidden from the package description, checkout and confirmation email.
Note: This will not prevent guests from being able to select their duration if the duration is variable.