Orchids should be re-potted every 12-18 months as typically the old substrate tends to break down and compact the delicate roots. In re-potting your orchids, you also provide fresh nutrients and allow the roots room to grow and expand, bringing new vigour to your plant and ensuring healthy leaves and long lasting vibrant flowers.
Most of the popular orchids seen today originally came from a habitat where they naturally grow on the branches of trees. So orchids don’t grow in soil, and you should never use soil or peat to re-pot them.