I was scared to order from overseas but these vendors are legit — looking for input

MariaRD said:

I would put less weight on the timescale, because two months of anything is not enough to distinguish a trend from a wobble.

This matches mine closely enough to be worth saying so out loud. I had assumed I was the exception until I read this.

MariaRD said:

I would put less weight on the timescale, because two months of anything is not enough to distinguish a trend from a wobble.

There is a second half to this that has not been said yet. The useful checklist is about verifiability rather than presentation. Independent test results commissioned by buyers rather than by the seller, consistency across multiple batches over time rather than one flattering report, a physical address and a company registration that resolve, batch and lot numbers on the actual labelling, and a shipping practice that matches what the material needs. Everything a good-looking website provides is cheap to fake; none of the items above are.

One concrete data point for the thread. The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the same conditions. Nobody wants that answer and it is still the answer.

Worth separating that from vendor vetting, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.

One thing that is still open after MariaRD’s answer:

How people are distinguishing a supplier having a bad batch from a supplier on the way out?

labquiet_amy said:

The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the…

I read this differently from labquiet_amy, on substance rather than tone. The objection nobody has made: this only works if the measurement is doing what we assume it is doing, and that assumption has not been tested here.