Very useful Rated 5 out of 5 stars

Thank you for making this excellent extension!

I have a suggestion to make it even better.
For remote calendars Lightning offers few options for calendar refreshing frequency (sync); it includes "every 30 minutes, 60 minutes or manual". Thunderbird freeze every time a calendar is syncing e such every 60 minutes frequency is totally unsuitable for most calendars, like holiday calendars, that hardly change.
Can you tweak to include additional refreshing options, like:
every 3 hours
every 6 hours
every 12 hours
once a day
every 2 days
once a week
every 2 weeks
once a months

The way to do it is shown here:
https://superuser.com/questions/591086/increase-calendar-refresh-interval-beyond-defaults-in-thunderbird-lightning