That is a good question but a hard one to answer as it depends on so many factors! These include the soil/type of soil used, how rootbound, how often you water, water hardness, temperatures etc. A slow growing plant in cooler conditions, rarely watered will be able to stay in the same pot/soil longer than a young vigorously growing plant in warm temps and watered frequently. In my experience the peaty soils like Miracle Grow do break down over time, and smaller plants, actively growing and watered/fertilized frequently benefit from repotting at least once a year. Larger, older plants in large pots may need less so. I know that may not be the firm answer you are looking for. As a guide if the plant is growing well and has healthy looking roots and is not too pot bound it is probably ok for the time being.

That was a good answer. Unless I see bad signs...I'm not going to change the soil.

Unless your plant is in really low light, it should outgrow any pot before the soil decomposes significantly, unless it was given a LOT of extra room initially.

Sometimes you can't tell if it's broke or needs fixing just by looking at what appears to be a healthy plant. Lost potential isn't always easy to quantify, but it significantly affects an extremely high % of potted plants ...... and when plants are the topic, lost potential can never be regained.

If you can lift the root/soil mass from the pot intact, the plant would benefit from repotting. That transitional stage of root congestion is about the point where limitations on growth and vitality begin to occur.

Al