If you are only getting an average of 2 months out of your units I can almost guarantee it is because of your shampoo.

Every now and then you might get a unit with very poor quality hair, but if this happens on a regular basis it has to be fixable.

My first couple of full caps shed to nothing, and I'm about 99% sure it was from a sulfate free "all natural" shampoo I bought at CVS. If it feels like wet cardboard when you are washing it, it's stripping too much moisture from the hair. A good hairpiece shampoo conditions as it cleans.