It's fine to do as long as you get new teats which can be bought separately. Unfortunately have to just bin the teats (unless they are new in packaging)
I gave mine to a friend that was expecting a baby however did tell her to change teats for obvious reasons, but if I did keep them as long as they was in good condition I would change teats and re-use x
I kept them but I have 2 under 2. I would probably get rid of them if I had a bigger age gap. New teats though!