Anecdotally I was told that when Air NZ stuck winglets on their 763's (soon to be replaced with 789's) they also sent them away to remove excess water from the insulation. The figure quoted was there was approximately 3000kg of water accumulated in each aircraft - more than made up for the weight of the new winglets.
They added a Zonal Dryers (made by CTT of Sweden) which added approximately 30kg in weight to save 200kg/aircraft. Removes excess humidity from insulation (from passengers exhaling).
Boeing elected to make it standard equipment on the 787-8/
9/10 and offers it as Buyer Furnished Equipment on B737NG, B767, B777, 787.
Airbus is also offering it as a customer option on the A350.
Flydubai has also installed Zonal Dryers on all their 737s.