I bought three old calendars on Etsy (from the fun, friendly Dime Store Chic shop). As you can see in the "before" photos, they were in very vintage condition. But, hey, if I was 110 years old, I might be crumbling a bit too. So I decided to "collage" them.
They are now mounted to illustration board so shouldn't crumble any more. Most of the elements I added are scrapbook paper. And the top one with the flag looks great in my patriotic bedroom which is why I bought them in the first place.
The third one will be heading to my Etsy store.