They have a clear format, all you have to do is gather data from a couple of legit SE's and you can determine the age of it.
By using estimatedly older links you can increase the chance of success.
Yet another note; you can search people's phone numbers and learn their location and give it to people who live in similar areas.
Once you have a large enough database of links you can easily give a link that has an incredibly close location to the buyer, meaning they buy for 1/4 of an SE and most likely will receive it, if not you give them two more links.
sorry, but this is bullshit. The replacement links are genned for EVERY account, even ones that have NEVER had a replacement. one of the capture keys is "mobile track" which is the app, and you cannot get the replaced so why would it gen a link for that.
The age of the link makes no difference because every fitbit account has one of these links even if they have never started a replacement with a representative. Therefore the odds of you bruteforcing an account in the process of a replacement are slim to none.
What is everyone doing for the photo portion of the links?
You change the color to make it not require photo. Or just take a photo/photoshop one.
Really surprised these links worked for my actually, but still weary since if my understanding of this is correct every time you do this you're sending the personal information to the real owner. Which means the risk depends on some random person which seems sketchy, not sure if any action would ever be taken aside from no product though.