Seeing the way at night is often not a luxury, but a real safety consideration. Having read a few comments in forums about how 900 lumens was not enough, I felt like a little more information might be really helpful.
Here's a few thoughts about what type and style of headtorch might be right for you. First of all I'm going to take you back... My first head torch, 1985 a Petzl Zoom. I can't explain the background of this torch any better than the article over at the Vintage Hiking Depot - well worth a read about the annual strap change... strap envy, never my thing, but was the original outdoor status symbol!
So this bit of kit, it took me around the Weald, along the South Downs, and an 'adventure' I'll come to. The excitement of being able to explore at night was amazing, frankly, at times the amount of light that came out was a questionable, especially when the moon was out. But, it shone the way on walks, runs, overnight camps and mountain bike adventures. The old 4.5v battery was a nightmare to find in shops, and had horrific plastic covering on, which I learnt to my cost on Number 5 Gully on the Ben is nearly impossible to remove with cold hands with no other light source. Another story entirely. The other bit was the 'bounce' of the battery pack in active sports - but it was ground breaking, and opened up more hours in the day for adventures. Hooray!
Flip forward 35 years and the technology, performance and choices are frankly astounding.
In my lighting armoury I have 3 head torches - here is my rationale.
At only 35g, I rarely head out anywhere without my Petzl Bindi with five settings (red and white) it produces a range of 'burn times' (the amount of time it will produce light) 200 lumens for 2 hours, through to a red emergency strobe for 200 hours. It's lightweight nature means I can comfortably have it on my head, round my neck or in my pocket, quick to hand. The adjustable elastic fits over a helmet or beanie. 200 lumens throws its light for about 30m, so perfectly capable to navigate down off a mountain, look inside someone mouth, make a brew with, or change a battery on another headtorch. It's USB rechargeable for about 300 cycles and is weatherproof. Any activity is made better by having a good torch as a back up.
My more regularly used torch is a Petzl Swift, Again, USB rechargeable for 300 cycles and weatherproof, but now with 6 white settings. From a huge 900 lumens down to 10 lumens. This comes with a burn time range from 2 hours to 100 hours. What does this mean really? It means at 900 lumens you can light something up 150m away (perfect for feature spotting night navigation, or descending on technical terrain) or at 10 lumens you can light something up 12 metres away (perfect for night time pees, or reading a book). This also has the benefit of 'reactive lighting' so a clever bit of electrical witchcraft changes the intensity of the light to be suitable to your needs. A bit more on that beneath.
Then, probably my favourite headtorch is my Silva Trail Runner 4x. It's mainly because it is a bit of a swiss army knife. It is rated as water resistant, so a little better for rubbish conditions. The battery options are the USB rechargeable battery, or a AAA battery box. This can be mounted on the head band, or tucked away in an inner pocket. The overall weight of the lamp is 49g and the rechargeable battery is 85g, or the AAA pack is 75g, so really light on the head with the units separated, great for running. 3 light settings are easy to use with gloves on, and give 350 lumens down to 50 lumens. The burn time depends on the type of battery. The rechargeable battery gives max power for 5 hours, or 50 lumens for 18 hours, the AAA batteries give max power for 30 hours, or 50 lumens for 90 hours. This means this torch, for times where you need light a lot packs realistically a solid 5 night times performance without the need for a recharge, and can be easily 'recharged' without a USB charger - a huge bonus for remote areas.
Some thoughts then.
How bright do I need?
On a clear night a brighter torch throws it's light further. so brighter is always best? I don't think so, how the light pattern is, and what you're using it for makes a big difference. 900 lumens on a map will take your eyes a significant amount of time to recover from. This is where the reactive technology is super helpful, dimming the light when the amount of reflected light is high. However, this too reaches a limit. In cold weather, where your breath vapour is thick, or inside a cloud, the light reflects back and this can be hard to work with. The Silva light bean is quite narrow, and this I prefer in snow, rain, cloud, but this narrowness means that the peripheral area needs more head movement to see. I rarely use any of torches on max bean for more than a minute or two usually when I am trying to locate something small in a 30-50m range from me.
How much burn time do I need?
This is simpler, the longer is usually the better, The flexibility of how a torch is lit, makes a difference how you are using it, but that's about it. The only thing to note is that temperature often makes a huge difference to the stated burn times. Silva state this pretty clearly - the difference between -5c and 20c is often double in medium brightness settings. For a remote battery pack, this is negligible because the battery can be kept warm next to your body, but for a head mounted battery the reduced burn time can be a significant consideration.
How much should I spend?
This is a tricky one, from many of the main names, there isn't really a bad torch. Alpkit do some great torches for under £20, where as you can spend £400+ on fully waterproof, bright, long burn time torches.
As with any bit of kit that is safety related, you have to be able to trust it to do the job that you're asking it to do.
I choose a different torch for different activities, in different locations, depending on conditions - and that only comes with experience. I'm not affiliated to any one particular brand, and am always more than happy to offer an opinion on things like this. Get in touch if you want some guidance.