Here at Linda Mason Designs.com we strive to create the high quality handcrafted items.  The materials we use are the best we can find.  Linda uses a high strength cotton cord for her necklaces and they should last a very long time, however, they may come untied with continuous use.  That is why we include instructions on how to tie them and also how you can shorten the cord if you like.  With continuous use (as we have found many customers do), the cords will wear out.  With that in mind, we will restring your necklace for free if you just send it and the beads back to us. 
If you are not happy with the quality or beauty of your one of a kind jewelry, hand felted or woven bag or any of the other handcrafted items we offer from Linda Mason Designs.com's web site, please send it back with an explanation and how to contact you.  We will address the matter to your satisfaction.  Of course, if the product has been damaged or misused by the purchaser, the decision of what to do will be at our discretion.  If you have questions please feel free to contact us here.