I've seen the film 10 times so far, and I too have kept all my ticket stubs. I thought it would be a good souvenir of this time. I do sometimes collect/save other stuff like that, but not regularly.
I have been fortunate to see my 10 viewings of BBM in 5 separate theaters, once each in 3 different theaters, and 3 times in another theater, and 4 times in the other theater.
And as a side note, it never occurred to me before to seriously consider the PROJECTION equipment/ screen/ sound system differences between theaters. I mean I knew in genera theaters had different standards, but that awareness was mostly on the decor and atmosphere, cleanliness, etc. This was the first time that I saw the same movie in several different theaters and so I had the chance to directly compare and realize that some projectionists have a better sense of focus than others! And some theaters adjust their sound to emphasize the ambient, while others nearly turn that off! And this last time I saw the film, the whole image was brighter and lighter, without any burn out.
Sorry to say, I expect this is the last week for BBM in my area, and by Friday it will be gone for good. Boo Hoo!
Jack in Maine