Bike lights

Buy an 18650 based pocket flashlight and a flashlight handlebar mount.

This is what i use for downhill riding at night.

https://www.amazon.com/sofirn-SC29-Flashlight-Rechargeable-Emergencies/dp/B0CP7BK3FF

Please watch out to orient your light in a way that it wont point into your fellow cyclists eyes. That can be very unsettling.

Bike lights often have optics that try to prevent this from happening off course only when properly oriented.
- I ride downhill mountain biking at night down super steep trails in the jungle. There is zero risk of another person being on the trail. But for sure do that if you're riding around other people.

Hub dynamo plus high quality LED lights from Busch&Müller, Shutter Precision or something similar. Will work forever and you never run out of battery power again.

I second the dynamo, never felt it pulling me back and I always have working lights. I tease my bike enthusiast friend whenever he asks to charge his lights but it really is just convenient. So far I've never broken them so I think that's a plus.
I used to be all about the dynamo, but I've moved away from it because it's so much easier to just take a battery bank if you need it. That way you only occasionally carry a small amount of extra weight, vs always having to pedal against a dynamo.
- A good hub dynamo has very low rolling resistance, so low that once the bike is rolling you do not notice it at all.

The best, longest lasting, but expensive route is a generator hub. Bonus, you can charge your phone, especially in the day.

Any number of torches can be used with a simple adapter. I'd recommend 18650 types, huge power, flashing modes etc., however there may be drawbacks

Honestly my experience has been that bike lights are way better with rechargeable Li-ion batteries, and not replaceable AA/AAA batteries. Every time I bought one that took replaceable batteries, they ended up, within a year at most, being incredibly faded and not working well, even with a fresh set of batteries. They get to a point where a brand new battery will work well, but for some reason where the first battery lasted months, the new ones all only last days.

I have no idea the chemistry/physics involved in this. It doesn't really make sense to me. Maybe rust on the contacts? All I know is that I've had this happen numerous times. Whereas my expensive combined light/camera unit with a built in battery has lasted years.

Might just be because that’s more of a feature on the budget side of the market, so they’re also made of shoddy materials in most cases.
Cooling is very important for LEDs. I've seen some cheaper brands skimp on the cooling methods, presumably because it means the product costs less to make, and may force a repeat sale later.

Something dynamo based if you want to keep it for life IMO

My current bike light is a bit of the opposite - a Towild DLite with a non-replaceable 21700 battery inside. It has a remote for the handlebar, so I can switch between the two beam angles to avoid blinding other pedestrians/drivers, and also functions as a USB-C powerbank.

Really hoping I can replace the battery when it eventually gives up the ghost - might need to 3d print a replaceable back for it or something

Power banks are much more efficient and effective than generator hubs anyway.

Just try to point it a bit more down at where you're biking rather than straight ahead, tired of having to wear a cap when I run at night to block incredibly bright bike lights

Busch Müllers are great such as IXXON Core. Also, I've noticed more and more people having very bright bike headlights that don't point downwards enough. They blind the hell out of me during my commute. Please do me the favor of orienting your light downwards and not pointing it into my eyes.

Nah there are plenty with replaceable rechargeables. You might be better off asking on [email protected].

I believe it's been recently discontinued, but the nitecore BR25 is one of the best I've seen. Removable battery, universal mount, shines light downwards so your actual bike is visible to others, has an excellent beam cutoff, and used to be relatively inexpensive (around or under $100).

The lack of replaceable batteries in most other lights is something I really despise.

Check out Fenix. I was super happy with my Fenix headlamp, so when the time came for a new bike light I was pleased to find they make solid options. Removable battery, good brightness, good adjustability to not blind others, used it road and mountain biking at night. Easily unclips from bar when you're leaving your bike locked up somewhere.

I think the most "BIFL" solution is a non-LED reflector. I've never heard of a battery device that lasts the lifetime of a bike.

It's a bit early to say "for life", but my cateye rechargeable lights are six years old at this point and going as strong as the day I bought them. My biggest worry at this point is that micro USB cables will start to get rare before the lights are a problem.

I've actually changed bikes twice in that time.

I'd sooner invest in a set of lights that stand out more than a set of lights with replaceable batteries.

For daylight usage the Exposure Lights Trace and TraceR set are amazing. But yeah, non-replaceable...

I haven't seen this but it looks ok if you don't mind the stupid UI. It uses a 21700 according to the PDF manual.

https://www.sofirnlight.com/products/sofirn-bs01-led-bike-light-teck

I would stay away from dynamo lights because they add rolling resistance.

Dynamo lights do add resistance, but unless you're racing, it doesn't really make too much difference. The bigger hurdle is the high cost of the hub
- I used to live about 3 miles from school, mostly very flat. It was nice to be able to coast through the flat part. The school was on a small hill. So to get home at night, I could roll down the hill picking up some speed, then coast the rest of the way. A dynamo would have used up that energy.

The good old "bottle dynamo" lights have stood the test of time.

No they haven't. Those were always shit and are absolutely not suitable for modern traffic.
- Maybe I've been lucky then. The ones I have had are from the 1970s and still work. They're also easy to repair, which in my opinion is part of making a product "buy it for life".
  
  I'm sure modern hub dynamos are better in lots of ways, but I don't know if they're repairable in fifty years.