I don't want to go OT here and perhaps this forms the topic of another thread but placing all the blame squarely on the reviewer's shoulders is mistaken. The manufacturer can demand the unit (s) being reviewed be returned--or paid for--at any time.
OTOH, let's take speaker reviews. Isn't it better for a reviewer to have several amplifiers (and you could insert cables, etc. here) around to use in the course of the review? Let's face it. Few reviewers are wealthy enough to own more than one amplifier.
I can't think of a single reviewer at both TAS, excluding Harley and Valin, and Stereophile, that don't own multiple amplifiers. As a matter of fact. most respected e-zine reviewers also own multiple amps. I did mean own.
I am far from wealthy, but I have a decent mix of amps to mix and match.