How do you know when a necklace needs to be restrung?
Necklaces strung on silk will need to be restrung periodically, depending on how often you wear them and the weight of the piece (pearls tend to be heavier so may need to be restrung more often than a light necklace.
Keep an eye on the silk. If it becomes stretched or discolored, then it is time to restring (before it breaks). Pay extra attention to the silk near the clasp — this is the area that takes the most wear as you open and close it.
If you get your necklace wet (caught in the rain, too much champagne escapes with the cork. . .), take it off right away and lay it out to dry on a light colored (preferably white or neutral) towel. When wet, silk will stretch very quickly, shortening the life of the silk, and making it much more likely to break.