A fellow mom who I saw always wore lovely necklaces, even though she had an infant that she was constantly carrying around. I asked how she had convinced him not to destroy her necklaces (mine always pulled on them until the clasps broke.)
She gave me a great tip that I am passing on - magnetic necklace clasps (you can get them on amazon http://www.amazon.com/Bluecell.....8&). They were originally designed for ladies with arthritic hands, but work equally well at preventing broken clasps from grabby baby hands. If the baby pulls on the necklace, it just comes off (annoying, but not destructive). They come in lighter weights for smaller necklaces- I also bought a stronger one for my heavier necklaces and it works really well.