Personally, I am a huge advocate for layering pearls because it is fun and complimenting to all!
When a woman layers her pearls she is asking for attention without being so obvious. Wearers of pearls are confident, charismatic and completely modish so to stack it them greatly makes them extraordinary.
To answer your question, I do not think there is such a thing of layering too many pearls but I do believe that there is a time and a place. You should stick to 1-2 pearl strand necklaces when at the office, and in other professional environments because you do not want your clients to focus on your jewelry rather than your business.