Go through the one and two-star reviews of any LED mask and a pattern shows up quickly. Not "this broke" or "this hurt", though those appear too. Mostly it's some version of: I've used it for three weeks and I can't see a difference.
That's not a product failure. It's an expectations failure, and it usually starts with the ad.
The honest answer
Nobody should promise you a timeline, because it depends on your skin, your consistency and what you're hoping to notice. What we can say is that anything advertised as visible in a fortnight is being sold to you optimistically.
Think in months, not weeks. Think in terms of whether your skin looks a bit more even and a bit more rested over a season, not whether something dramatic happened by Friday.
Why consistency beats everything
Ten minutes three or four times a week, kept up for a few months, is a completely different proposition from an enthusiastic fortnight followed by the mask living in a cupboard.
The cupboard is where most of them end up. That's the actual reason people don't see results, and no amount of wavelength engineering fixes it.
So the practical advice is unglamorous. Put it somewhere you'll see it. Attach it to something you already do every evening. Ten minutes while a podcast is on beats a heroic half hour you'll never repeat.
Take a photo on day one
This is the single most useful thing you can do, and almost nobody does it.
Same spot, same light, same time of day, no makeup. Front on and both sides. Then don't look at it again for eight weeks.
Skin changes too slowly for you to notice in a mirror you look at daily. You will genuinely not be able to tell. A photo from two months ago is the only honest comparison you have, and it's free.
What to be sceptical of
Any brand promising results in days. Any before-and-after where the lighting has obviously changed. Any claim to treat a named condition, which in Australia moves a device into a different regulatory category altogether and most brands making those claims haven't done that work.
And if nothing changes
Then it didn't work for you, and that's a legitimate outcome rather than a failure of persistence. Some people love the ritual and would keep doing it regardless. Some try it for four months and conclude it wasn't worth the money.
Both are reasonable. We'd rather you reached either conclusion honestly than kept going because a brand told you results were just around the corner.
General information, not personal advice.