Question about stickers

This is purely out of curiosity, since I've been and on again/off again player for years but I've never played this time of year.

For a few days, the part of the shop that sold the stickers was full of so many different designs that normally aren't there. This included stickers that seemed like they'd been for different events from this year, which I'm assuming were stickers that were limited time.

However, these stickers are now gone, and the seasonal and generic ones are the only stickers left.

Is this something that happens every year? Where for a limited time, stickers from all the seasons and events for the past year become available again for a limited time? Or was this some fluke that has happened for the first time and may or may not happen again?

Thanks!