Nipple Sensitivity

My girlfriend used to have very sensitive nipples when we first start going out (in a very good way) and now, 12 months later they dont do much for her at all.
Is this common, any ideas?

 

Maybe you played with them too much.

 

Nipple sensitivity differs from women to women...some women like nipple stimulation, some don't. Some have very sensitive nipples, some don't. Not enjoying nipple stimulation does NOT mean there's anything wrong with you.

 

Did I miss something? I didn't see where the Op said his girlfriend had implants.