My cactus is seven feet tall. I've had it for about 20 years. There is more brown color at the base and up two of the stalks but it continues to make new baby leaves all over. It is in a pot that is 8 inches across. I'm concerned that it might need to be repotted but there is no way I can lift it. Also I wonder if it's too dry or too wet? It sits by the window that faces south and a large picture window on the front wall faces east. Please advise.