So, it turns out that the reserve fleet has another benefit! This from Guildleader Steve Fallingbridge's site:
In other words, the Shadow Guild members can now receive five years without dues instead of three. Very nicely done, Steve!
But since the Shadow Guild has completed their fleet for some time and we're only now hearing about this, it's a likely conclusion that this is a new benefit, solely for guilds with a complete reserve fleet.
Which brings the next question: what other benefits are around the corner?
And who else is going to be next to have that reserve fleet finished?