Rated 1 out of 5 stars

Following up some other previous comments, I'm obliged to rate this add-on very poorly due to the wrong design philosophy.
When syncing with a remote calendar the application loads all the events (1000, with no option to set less), but if TB is restarted the whole syncing process restarts.
This design choice is maybe not an issue when you have 2/3 calendars with a total of few hundreds events, but when your company is using google calendar events and you have dozens of colleagues all having 1000 events to share, it all becomes completely unusable.
On top of it, the syncing process is started without any user prompt, so TB is completely non responsive, making it worthless.

While I appreciate the overall idea behind, the implementation is so rotten that I can only wish in a major rework.

This review is for a previous version of the add-on (1.0.4). 

Before commenting on the design philosophy, maybe you should read the code to confirm that this is actually the design philosophy used. Quite unfair to leave this kind of comment based on a few observations in the UI.

On the first synchronization, the Provider for Google Calendar downloads all events from the remote calendar, in batches of 1000 (hence the number you are seeing). It is not clear how many events are in the calendar at this stage. Once this batch is through, the next one is started, which also displays as xxx of 1000. Admittedly, I could display this differently by not always showing xxx of 1000 but jumping to 1001 of 2000. There is an advanced option to change the batch size, but this is not necessary.

Once the initial synchronization is done, the synchronization token is saved locally and all future synchronizations are incremental: only changed events are downloaded. So, let me guess, this is exactly how synchronization software should work? Yes, I thought so.

That said, what is happening in your case is probably that the initial sync is not complete, hence the token is not saved on shutdown and next time you start up, it attempts to start over. Please give it some time.