The Mechanical Race's mothership differs from the Empire's Dusk's main ship in several ways.
The mothership of the Mechanical Race also serves as a mobile factory to a certain extent.
It can use the factory to manufacture war supplies and various Mechanical Race units, and can also utilize the factory for self-repair.
As long as supplies are adequately prepared, the Mechanical Race's mothership can operate for a long time without needing frequent port visits to replenish war supplies.
Unless supplies are depleted or it suffers significant damage that cannot be self-repaired, it generally won't return to the giant docks or maintenance centers.
The reason the four motherships landed this time was due to Chen Ming nearly exhausting their supplies with his hundreds of thousands of Insect Race cruisers.
Chen Ming needs to create more opportunities that force the mothership to act.
