Is polymerclay fragile?
If well cooked, absolutely not. I have items from years and they are perfect. Obviously you should pay attention to your necklaces, and you should avoid to water your objects.
this applies to all handmade objects ;)
necklace charms : 2 inch
earring/ bracelets charms: 1 inch
studs dolls: 0,5 inch
necklace length: 19 inch