If you're having trouble sleeping on your gel mattress, it might be time to replace it. Here's when you should do it:If you're sleeping on your mattress less than six months per year, it might not be time to replace it. However, if you're experiencing pain or discomfort, it might be time to replace your mattress.If you're sleeping on your mattress more than six months per year, it might be time to replace it. If you're experiencing pain or discomfort, it might be time to replace your mattress.