New convert to Nepenthes

[alpexec]

I had a Nepenthes Allata (so the label says!) as a gift last summer. It has thrived in my conservatory until the cold weather arrived when it was moved into the house. I repotted it after about 2 months into sphagnum moss and it has never looked back. At the moment it has about 20 pitchers in various states of freshness from very new to old and withered. As a complete novice I am unsure what to do with the withered parts - do I cut them off or leave them to decompose naturally. Any advice would be welcome. Thank you.
PS I apologise if this subject has already been covered in another thread.