I have late teethers, mine have cut them at 9 months, 8 months and 11.5 months respectively. Apparently average is around 6 months but I have known plenty of babies that have cut teeth around 3 months. Every baby is different. I would say if they have actually cut and you can feel the sharp edge they will be out for good. I find with mine that they can go up and down a couple of months before they actually cut as in you can feel bumps but no sharpness. But once I can feel sharpness they are cut for good.