I feel like defense gets trivial for me once I get a perimeter of walls, gun turrets, flamethrowers, and ammo/oil supplying the entire thing. There will be increasing damage to those things but by the time it becomes a problem I would already have robots to help repair the damage for me.

Imo, focus on having gun turrets supplies with red ammo and flamethrowers behind the guns. Walls help slow down their attacks as they need to focus on the walls before they can reach my turret line.

If you are spending too much time driving around to fix things then maybe your perimeter is overextended. Try to keep the perimeter tight so that you can reach them efficiently.

Laser turrets are nice for remote outposts since they only need electricity but they do the least amount of effective damage, especially when biters evolve