I am not a fan of store bought advent calendars as most of them are just filled with cheap chocolate and even cheaper trinkets. 

While the idea of having a countdown to Christmas is great I have always felt that there is a better way to do advent calendars.

Though advent calendars sounds like they are an ancient custom they have only really gained popularity since the 1950's. Being a relatively young idea I think that you should be able to customize it any way you would like.