If you wear your pearls quite often then you may want to consider getting your pearls restrung once a year. If you do not wear them that often, then restringing your pearls every 2-3 years is fine.
You will know when it it time to restring your pearls when there is space between your knots and your pearls can move around freely. Also, if you find that your knots are looking soiled, then it may be time to consider getting your pearl necklace or bracelet restrung.
Either way, when it's time to restring your pearls, we have the experts.