I've taken to try a new strategy. The AI can only reinforce between 8 and 30 planets (at least on difficulty 7) at a time. Because of this limitation, what if I attrition the AI player? Rather than allow them to do it to me, I jump into a low level system and establish a beachhead. A bunch of turrets covered by counter-sniper rifles. This works best when the merchant is visiting, then I can put up a force field and and build an ion cannon (or cannons) under it. Thanks to the large health of remains rebuilders, they can happily rebuild turrets that are worn down and survive a bit of a beating, and will sit cloaked regenerating otherwise.
The AI in turns sees this presence as a threat and reinforces the system. The ships generally die quickly to the established beachhead, especially so if an ion cannon is involved. The important point is that the AI is not reinforcing other systems because of this. At first, the AI will do a 4x reinforce on the system, but as the player spreads out more of these beachheads are required, and they in turn become easier to maintain. But at this point the AI is generating even less ships. Now when the player invades, the AI won't have many ships to defend with, and a few casual raids will have long lasting effects on enemy forces. By establishing a permanent presence on an enemy planet without wiping that enemy out, that enemy planet becomes an asset without having to hold it. This strategy also seems to apply to warp gates. A system with a warp gate will get flagged for reinforcements, and with only a few turrets around the warp gate, the interlopers can be dealt with. This saves on AI progress by not killing those and further reduces their ability to reinforce other systems.
As a casual benefit to this strategy, more energy reactors can be built in the established beachhead to avoid the costly energy reactor 3s.
Has anyone else tried this strategy, or want to give it a test run and compare it to other strategies they have tried?
Thus far I've noticed the game become significantly easier after establishing a few of these, as now the enemy no longer rushes me as much and rebuilds much slower after a failed raid. Though turrets, since they no longer require reinforcements to replace, can still be nasty.