Wait, the Great Collapse didn't take place in PS III, but on Motavia. The Alisa III was having its own mess at that time
Checked all the timelines I could find... now I'm more confused than before. According to the PS4 script, we learn that:
-A thousand years ago, our society was thrown into confusion by the
destruction of Mother Brain. After that, Motavia sustained a
direct hit by a fragment of the exploding planet Parma. Our
civilization was almost destroyed. We call this 'The Great
Collapse.' ...Oh. I didn't realize you weren't students.
-Once, there were three planets in the Algo solar system, but during
The Great Collapse, the planet Parma was lost. Now only Dezolis
and this planet remain.
-From the prologue:
"Then a series of disasters struck.
The system-wide managment system, 'Mother Brain,' was destroyed.
So was the first planet, Parma.
Over 90% of the system's population died, and the advanced technological
culture was lost.
Society declined, spiralling downward until at last only a few scattered
groups even remembered there once were better times."
So... my guess would be that the Great Collapse starts with Mother Brain's fall, and spans for an uncertain ammount of time. I would say it would take 50 years or less for all the survivors to die and leave the following generations clueless about the past knowledge. Or less if we consider that most of the scientists and technicians died during it. However, some capable people had to survive, as Daughter and Wren were made. Alright, Daughter could have been built while Mother Brain was "alive", but since Wren's 998 years old, that tells us that he was made during the Collapse...
Any other ideas?
PS: Edge, I don't think the Collapse spanned through PS3 because we still don't know when it really takes place, and if we consider AW 2292 correct, it would include PS4, which happens at AW 2284, according to its script