Answer: Generally speaking you would move to the next larger container size and use a potting mix that is a close match to the texture of the original so they drain similarly. Many gardeners prune their hibiscus to control the overall size to avoid having to eventually move to a huge container. You can prune it back quite hard all at once in late winter or early spring (can cause a time lag before it blooms again) or prune selectively year round to remove just the longest branch or two from time to time. You can also refresh just the top inch or two of soil in the container to avoid a complete repotting.
When the hibiscus is actively growing during the summer and outdoors it will need more water (and fertilizer) than when it is less active in winter. Water when the surface dries out to keep it evenly moist during the summer. In winter you might allow it to get a bit drier between waterings, especially if it is in a relatively cool room. If you have had a for a long time you probably already have a feel for when it needs to be watered.
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