Veneers should last for many years; but they can chip or break, just as your own teeth can. The bottom line is that your veneers will eventually need to be replaced due to leaking, chipping, discoloration, decay, shrinkage of the gum line and damage from injury or tooth grinding. Other options may include bonded composite restorations which work a bit like veneers.
If possible, we would bleach and/or straighten your own teeth instead of using veneers as long term this is a better option. In certain cases where a tooth is discoloured due to a root treatment or previous trauma, internal tooth bleaching might be an option to improve aesthetics on its own, or to improve a veneers “background” colour. Come in to speak to us about your options.