Sever’s disease (calcaneal apophysitis) is a common problem with the heel bone in children and will typically last anywhere from weeks to months or longer. There is no predictable pattern or time frame. If activity levels are reduced to a very low level and things like cushioned heel pads used, this might reduce symptoms in a matter of weeks but they could recur when activity levels are increased. If there is a small or no reduction in activity levels so that the pain is tolerable by the child, then it may last months.
The growth plate at the back of the heel bone where Sever’s disease affects the foot will merge with the rest of the heel bone by the mid-teenage years, so it will no longer be a problem after that age. Up until then, it is a matter of managing activity levels and loads on the heel bone so that the symptoms will eventually clear. This can be a long time in some children.
See this PodChatLive on calcaneal apophysitis: