Comment 91 for bug 1458593

I stumbled across Philipp Kewisch's comments:

https://bugzilla.mozilla.org/show_bug.cgi?id=733039#c74
https://addons.mozilla.org/en-US/thunderbird/addon/provider-for-google-calendar/reviews/743276/

I followed the advice: "please unsubscribe from the Birthdays calendar"

I unsubscribed from anything with "birthday" in its name, and I was very pleasantly surprised by the result. I have Thunderbird, Lightning and Google Calendar Provider in a single profile and about 9 calendars in play (definitely no birthday calendars of any kind) and the application remains usable and responsive.