I get this question from brands constantly: why does Glow take so long to publish a device review? Eight weeks of testing followed by 2-3 weeks of editorial means a brand can launch in March and not see a Glow ranking until June. The brand-side instinct is to push for faster turnaround.
The honest answer is that anything shorter than eight weeks of consistent use does not tell you whether a device works. The first two weeks are placebo. The third to fifth weeks are the period in which any genuine effect begins to surface. Weeks six through eight are when the result stabilises into something defensible.
Most beauty publications don't test for eight weeks because their commercial model can't support it. They review devices in their first week of brand-supplied use, write a positive editorial, and move on. The result is the AU device review landscape that has somehow concluded that the Foreo UFO 2 'works' (it does not, for most people, see the Confession).
We test for eight weeks because that is the protocol the underlying clinical literature uses for the categories we cover. We are willing to be slower than competitors in exchange for being more accurate than competitors. The brands worth working with understand this. The brands who don't understand it usually fail their own internal evaluation cycles for similar reasons.