PlantLife Online

Answer

Most plants will do well in pots for 2-3 years before they become root bound and unable from retain moisture. You will know when you water the plant and water quickly drains out the bottom of the pot. When this happens there most likely is little soil reming and most of the pot is full of roots, time to replant either in a larger pot or in the ground. You can also check by digging down with your hand and looking at the roots.

If you're referring to the black plastic pots shrubs come from the nursery in they will do ok for months with the proper care however the sooner they are planted in the ground or larger pot the better.