Konrad von Richtmark got a reaction from Talon of Anathrax in Are there really 300+ year olds roaming the Imperium?
If memory serves me right, the official adventure "Rejoice for you are True" from Purge the Unclean for DH included a mention that a juvenat-user will, after some 150 years, look fairly amorphous and featureless in the face, after which it's not really possible to tell their age from their looks.
Konrad von Richtmark got a reaction from Decessor in Should all Rogue Trader Ships have a Navigator?
NPC navigator is definitely the way to go, but letting him roll against a "base" crew skill value of 30 is just a recipe for recurring disaster. I did it by generating a navigator character using the core character generation rules, spending starting xp sensibly, but froze character development after that (as NPCs aren't supposed to become better over time).