That's a nice run through Guy. I know I've read these speculations on the timing before but I always forget how long it's been since they had space travel. They either really hit a wall (perhaps the atrophying of curiosity was their undoing?) OR at some point most races just plateau and advancements become less about faster and bigger. Because they've spent seemingly many thousands of years with not much development. Of course if you see no point in exploration you're not going to be urging your species into dangerous new territory. Maybe the big adventure of repression slowed them significantly.