At my grocery store they used to do periodic monthly discounts on bills for 3/5 days.

4 years ago every 25€ spent you got 5€ discount - 20%

3 years ago every 30€ spent you got 6€ discount - 20%

2 years ago every 30€ spent you got 5€ discount - 16.6%

Today I got one that gives 6€ on a 40€ total spent - 15%

.. I also just noticed the discount is available only for 3 days now..

Thankfully I acted accordingly since 4 year saving in #bitcoin.