When Baby can sit
One simple way of approaching weaning from a bottle is when ever the baby can sit alone.
Then it is an ideal time to wean to a cup.
If you are weaning from the breast, there are more factors to consider, there are time constraints if you are returning to work, do you have the energy? Is your baby ready?
Are you ready to stop nursing. When ever you and your beby decide it will be the right time.