I know the purpose of fleet upkeep is to prevent players from camping and not using big fleets. The thing is it created even more problems.
In late game gameplay resource aquisition can get painfully slow because of having a big fleet. And it can prolong and already decided game, because orbital defenses dont suffer fleet upkeep.
An already defeated player can still withstand a superior player by solely relying on gausses and hangars because he dont suffers the upkeep the attacking player has with his fleet.
Fleet upkeep has its purpose, but it adds to the prolongment of games. It should be lowered.