Zoom Webinar on-demand option

Welcome to the Zoom Community, @chichichi1.

Check to make sure your cloud records are NOT set to auto delete (Settings -> Recording -> all the way at the bottom:

This means your recordings will stay as long as you have your account.  If you want most of your recordings to be deleted in 30 days, but keep just a few of them... then you'll have to start manually deleting the ones you don't want to save.

Now for the registration piece:  I haven't researched this, but I would think that as long as the recording is still on file, Zoom will continue to allow "registrations" to watch it.  Since the registration is to the recording, and not to the webinar itself, as long as the recording URL is still valid, it should take registrations.  Again... not tested, and I couldn't find a specific document to confirm this, but I'm pretty sure of it. 😎