the last major model/texture update on ships was done in 2007 (I am not speaking about the small technical updates they usually do with their engine, or the constant changes to ship skins, etc).
The recent "changes to ship skins" are more than a paint job. The textures have been significantly revamped at the same time to improve lighting.
Yep, and they have not changed any graphic assets, and they are still the same since Trinity for ships and structures. Same quality textures with minor tweaks, same 3D models with minor tweaks, etc.
Their last changes were done on the engine side mostly.
Of course they have done a lot of major changes on other things since Trinity : planets, turrets and missiles... That's maybe the only MMO I have seen to rework on their graphics so extensively.