It is generally recommended to repot plants soon after buying them, especially if they are root bound or if the potting soil looks old and depleted. Here are a few guidelines for when to repot plants after buying them:
If the plant is root bound: When a plant becomes root bound, it means that the roots have become so crowded that they have filled up the entire pot and are starting to circle around the inside. This can restrict the plant's growth and make it more prone to stress and disease. If you notice that the roots are starting to circle around the inside of the pot, it's time to repot the plant.
If the potting soil looks old and depleted: Over time, potting soil can become compacted and depleted of nutrients. If the soil looks old and depleted, it may be time to repot the plant and give it some fresh soil.
If the plant has outgrown its pot: If the plant has outgrown its pot, it may be time to upgrade to a larger pot. This will give the plant more room to grow and allow its roots to spread out more.
If the plant is struggling: If the plant is struggling to thrive, repotting it may help. Sometimes, a change in soil or pot size can give a struggling plant the boost it needs.
It is generally best to repot plants in the spring or early summer, when they are in their active growing phase. This will give them time to adjust to their new pot and soil before the winter months.