Okay, correct me if I’m wrong:

In the Pathfinder Universe, souls travel along the River of Souls after death, then hang around Pharasmas Boneyard for a while, get judged and then get send to whichever Outer Sphere plane matches their alignment.
There, they become so-called petitioners, suffer/enjoy themselves for a while and with sufficient piety/malice/effort, eventually turn into a plane-appropriate outsider. 

Now, has is ever been stated how long this process roughly takes? Years, decades, centuries, millennia? The only reference to time I found was about hammer archons:

> Those archons who continually proves themselves in battle, either by
> striking down hordes of demons or by holding back a single pit fiend
> long enough for reinforcements to arrive, may get promoted to the rank
> of hammer archon. **This process can take centuries, even millennia,** but
> the lawful-aligned outsiders would brook no shortcuts. Many hound
> archons and shield archons with martial inclinations ceaselessly
> endeavor to rise to the heights of power that being a hammer archon
> represents.

But this is more about “rising in the ranks”, so to speak. And “brook no shortcuts” implied that shortcuts are apparently a thing(?).

(Honestly, the most interesting question to me is – would it be feasible for someone’s wise old mentor figure to return as an archon or for a former BBEG to reappear as a devil? I know they don’t really keep any proper memories of their old selves, but it would still be cool!)