I have a supply-train running to all my outposts, delivering the needed spareparts like walls, repairpacks, turrets, and mines.
Usually a biter attack only destroy a few mines so once they#re set up, you rarely need to replace more than 30 or so.
Edit:
Since the Aliens kept bothering me (and growing homes directly in front of my bases) i startet to build the great wall (without mines yet)
All walls are 3x2 wall-lines, defended with a line of laser turrets, backed up with roboports.
Supplies are brought from my mainbase via trains( walls, repairpacks, turrets).
Each wall have a single passing-point for further expansions.
Im almost finished, only the north-western wall is missing
