My belief was, under CCR you had 14 days from receipt to effectively just change your mind for no reason. Limitations on this include
something that deteriorates quickly – like flowers or food
an item that was personalised or custom-made
anything from a private individual rather than a business
a CD, DVD or software, if the seal is broken
Pierced earrings and other items that are unhygienic to resell
but that doesn't seem to cover motors. Same way you can return clothes, etc. I'd imagine there's some stipulations on them being undamaged.
Putting that aside, it should be relatively easy to test them on return to see that they are, indeed, still working. They've probably had more usage going through initial QC...
Additionally, they give a year's warranty on it which makes you think it's pretty robust...
I did, but it was medium which isn't up to the job (to be fair, they mention recommending Red as a minimum, but I was using generic threadlock described as "medium"). In the meantime I have ordered some Green. Which does mean I'll need a heat gun if I ever want to take it apart again.