Each of them adds a 10% leader quality bonus, which adds up, when you have 150 of them (1500% bonus).
This leads to new leaders with skills in the 40-50% range.
One of those skills is ship maintenance reduction. There are other sources of this, which also add up, to potentially (and I regularly see this happen) beyond 100%, which currently means I am making money from having my ships maintained.
Which means, the more ships I have, the more money I make.
This is nice, but hardly right.
The way I would go about solving this is changing the maintenance formula to something like:
Actual maintenance cost = Base Maintenance cost /(1+reduction bonus).
At low bonus percentages, this works very much like the conventional Amc = Bmc*(1-bonus), but however high you go, you will never make money from having your ships maintained. Plus: diminishing returns.
Of course you can tweak this formula to your hearts desire.
And you can implement it in other potentially troublesome areas, or just across the board.
You can also ignore it.