Relevant rules snippets from Run & Gun, p. 59:
These items are the most recent incarnations of their corporate creators. That means they lose a little more when purchased as Lightly Worn, namely a 20 percent loss of Armor Rating (round adjusted Rating up) when buying older models of the clothes.
The Lightly Worn option provides runners with a chance to buy some primo gear at a discount rate, with a few catches. Buying from the Lightly Worn section requires the character to have Armand as a contact with a Loyalty of at least 2. When gear is purchased Lightly Worn, the character gets a price discount of 25 percent, but they only get the Armor rating; they do not get any of the Features of the armor. The Lightly Worn feature can be bought off by having the piece of Armor refit. This requires an Armorer + Logic [Mental] (10, 1 hour) Extended Test and costs 10 percent of the original armor cost for each Feature the character is trying to have restored.
Do I need to refit a Newest Model every so often to avoid having it degrade into Lightly Worn and lose 20% of its armour rating? Or is Newest Model only meant to imply that purchasing the used version gets you an older model that isn't as good, and applies the -20% armour rating in addition to Lightly Worn's lack of armour features?