Utility is an economic term for a person's overall well-being and satisfaction. Consumers play a role in the economy by maximizing utility, which means allocating their scarce resources, such as limited time or money, most efficiently. Utility maximization is different for every person.
You can start using it right away but it was suggested to us by our midwives to hold off until 6 weeks as pacifier use can mess with their breastfeeding latch (it's a different kind of sucking).
Parents often start toilet teaching when children are about 2 years old. If your child had a low birth weight or is developing slowly, you may want to wait until closer to age 3. These are the ages when children usually develop toilet skills: Age.