I've only tried one brand of henna. I liked it so much I became a trainer for them.
I've tried so many different brands of peroxide activated tints that I've lost count. I also train for a brow shaping brand - they don't think there's much difference between tint brands either.
What I have noticed is that tint lasts different lengths of time on people. Where you are mixing up more than one colour, the mix can affect longevity which a hairdresser learns about but a beauty therapist doesn't. I've noticed that ethnicity seems to play a part in longevity as well. So there are factors outside your control which can affect how long the tint lasts.
So I quote 2 weeks for normal tint but say that it varies from person to person. I also say that tint lasts overnight on me, which is a quirk of my ethnicity and that some people say it lasts for a month. Lucky them.
Henna on the other hand lasts really well, that's why it's so popular. I'm sure it varies from brand to brand, but it outlasts peroxide tints. On me, Mina henna lasts 3-4 weeks. I start filling my brows at 3 weeks with make up, but I can still see the tint on my brows. I quote 4 weeks for a return appointment.
The staining on the skin is akin to fake tan, it wears off gradually. The more you cleanse your brows the faster it'll wear off the skin. You could scrub the skin stain off if you really hated the effect. The point of the look is that it gives you a natural brow. The over made up Instagram brow is still very popular of course but it's no longer the latest look.
Im really happy with the Mina Henna colour range, it's superb with the blonde colours which surprised me. The colour is very intense, yet natural and the henna makes the hairs glossy which sounds weird, but it makes the colour really pop. But not in an over done way
Henna lashes look lovely, but it's a really stingey product. I'm selective about who I use it on, some of my clients scrunch their lashes tight shut and I wouldn't use henna on them, because it's left on for quite a while (with my brand) and it wouldn't be tolerable if you'd made your eyes sting in the first 30 seconds.