The breast is an amazing organ, and as the months go by, breasts are less and less prone to problems such as engorgement, plugged ducts, or mastitis at time apart from nursing. That depends on your toddler and you. Many will self wean if you direct a weaning strategy of not nursing except upon request. Others may need encouragement if you decide you are ready to wean before they do. Just be sure to let the weaning take place slowly, and expect a few setbacks along the way.
Most moms report that it is easier to wean an older child than a younger.
I can see the advantages of nursing an older child, but I'm planning on returning to work. Actually, it's very easy to continue a nursing relationship with a toddler and go back to work. Because the breasts are less prone to engorgement, most mothers can simply nurse in the morning before leaving and as soon as they get home. Moms who go back to work early simply begin dropping pumping sessions as their toddler begins solids and other liquids. Moms who've gone back to work and continued nursing tend to feel better about their work experiences, knowing that they are still providing their baby with the best, despite being separated for part of the day.