The Forerunners

Lately, I've been browsing the wiki, coming upon many articles regarding the Forerunners and their technology. Through this a few questions have arisen. Why didn't the forerunners take refuge on the remaining shield worlds when they fired the Halo rings? Why didn't they shield their home planet? Why weren't they catalogued for reintroduction? The forerunners definitely could've built more shield worlds, the Lifeworkers and the Builders had similar beliefs, so one would think that they would know that Halo would be fired and would erect more shield worlds to sustain Forerunner populations. And if there wasn't enough time to erect that many shield worlds, they could've at least shielded their home planet. And they definitely could've catalogued themselves as a fail safe. Please, tell me what you think!