I love it when my kids can find something quiet and non-destructive to do to entertain themselves. Though sometimes I do wonder if this kind of repetitive behavior is normal. You should see what she does with blocks.
We had to get rid of all the really small elastics (the half-inchers) after I caught her with dark-purple hands a few times.
She had already moved all the elastics onto one hand before she started the transfer to the other. I wanted to see how long it would take her--in real time, five minutes. The soundtrack is "Bagdad" played by Lissa.