FWIW, I once had over 6500 reviews outstanding. I ended up resetting from level 60 to level 46 (which reduced the peak review load to around 5300). After that, I just spent years slowly grinding it out, no reorder or anything (I’m sure that would have made things a lot easier if it had existed at the time though).
This is also true. My second time through WK was a lot easier than the first because I already knew some of it well just from natural exposure.