[Nytingale]

I've checked it out with another person in-game (Finally! The number of people who don't use Maintenance is baffling!) and they basically confirmed the same thing: Self-Service does not account for upgrades to a weapon's durability, it seems. As for the case of my Hahouken Masterwork Katana? I'm still trying to figure that out, as it seems to always gain +1 Durability even without me having Self-Service, and does so until it reaches 19 (I previously thought it was 18, but it's really 19, it seems).