If you want to allow different import periods to the same feed type, you have to create clones of feed types, making the site unnecessarily complex. Furthermore, the user creating the feed of that type, doesn't know about the import period.
Create a feed type and be forced to select an import period.
Create a feed of that type and you can only make the import active/inactive, without even knowing how often that would run (depending on your permissions you could see this on other admin pages).
Make the import period setting visibile on the feed form.
Add an option in the feed type form to allow selecting (overriding) the import period on the feed form.
Add the permission to change the feed import period on the feed.
Active
3.0
Feeds Import (feature)
Related D7 issue: #1984982: Allow sources to override the import period →