It's important to try to take the sippy cup away by diverting your child's attention to something else or substituting a teether or some other toy. You can also make sure that the cup is used only for feeding times or drinks in between, but the parent retain control of the sippy cup. If your child is permitted to carry it around with him/her all the time, it's more likely they will be tempted to chew on the spouts.
This happens with any soft spout regardless of the brand of sippy cup. It's important for the parents to check the spouts regularly to make sure they are not getting discolored or worn, or have any tears in them. The replacement spouts are readily available and this is such a short time in your child's life that having plenty of the Nuby wide spouts on hand is a temporary expense, but a safe choice.
The Nuby wide spouts are great spouts for your baby to transition from bottle to sippy cup simply because they are made of 100% medical grade soft silicone. You can purchase various quantities online at http://www.shop.nubysippycup.com . Although some of the major retail stores like Toys R Us, Target and Walmart carry the cups regularly, the replacement spouts are rarely seen in the stores.