Rated 5 out of 5 stars

Lightning only allows users to refresh their remote calendars (in my case Google calendars) manually, every 30 minutes or every 60 minutes.

These short refresh intervals and the inability for users to choose longer refresh intervals is not helpful because when a refresh takes place Thunderbird freezes completely, I can't even read my emails properly. If this happened every hour I'd go mad.

So, for years, I've resorted to just syncing my calendars manually from time to time, whenever I think of it.

Now this add-on has come to the rescue! Finally! After you install it and restart Thunderbird, when you rightclick on a calendar in Lightning and choose Properties, under the Refresh Calendar dropdown there is a new option (under Manually, Every 30 minutes and Every 60 minutes), called Custom.

Select Custom and now you can input the refresh interval you want for the calendar, in minutes, and it seems to allow very long intervals (in one case I've made it 2880 mins for a fortnightly refresh, for instance). You have to do this for each of your calendars, but you only need to do it once per calendar and then it's all sorted.

Wonderful! I've been wanting something like this for years. This is not a new issue, others have requested this feature, or at least the ability to choose refresh intervals every few hours e.g. 3 hours or 6 hours not 1 hour max, but nothing has happened with Lightning itself, so this extension is a real godsend. Now I can achieve a much better balance between too-frequent freezing and ensuring my calendars are automatically synchronised.