Here are some flashlight tips more on the side towards preparedness / battery usage:
Standby flashlights
Many of us have several lights fueled up at any time, but how many of them have fresh fuel, ready for a power outage or other emergency situation?
Choose a few of your lights that you don't mind using only occasionally to be standby lights - 3-5 would be ideal. These should be quality lights you would be happy to rely on if you did not have your EDC (or it was broken). For some of you, shelf queens might make good standby lights. If you have trouble selecting them additional criteria for me are lights that are single cell (AA, AAA or 18650) and have variable brightness levels. Lights with very high parasitic drain should be locked out however a little bit of parasitic drain is fine.
Leave a fully charged cell in each standby light and place them in a dedicated place. Don't scatter them about, perhaps select 2 locations. Every month or so swap your EDC with one of these and use it until the battery runs out. Then recharge the cell and place the light back into the standby pile. Other than that, try to avoid using lights from this pile unless your EDC/primary lights are out of action or it is an emergency.
This ensures that you have a set of "grab and go" lights that will always work when required, have a fresh charge, and that the batteries get cycled reasonably regularly. Secondary cells work better for this because ideally you will use the light every month or so to ensure it still functions correctly. If you use primary cells this could get expensive.
Weekly EDC battery topup (mostly 18650 lights)
If your EDC light uses a lithium-ion battery, get in the habit of checking the power level every weekend. Once you are below about 60% charge top up the cell. You will be confident knowing that you always have at least half a tank ready to go if the unknown strikes at the worst moment. This works better for lights that use a high capacity 18650 cell, as even half a charge would be plenty for most power outage situations.
If the cell is around 80% or so, I usually wont top it up as I want to increase the lifetime of the lithium-ion cell a little bit. However if bad weather is rolling in, you might want to top them off anyway
USB "desk lamps" / plug in lights
If you have any USB power banks, buy a couple of USB lights for them. Make sure to get at least one long-running laptop keyboard style light (good for reading/playing cards) and one high power one.
The low power ones sometimes draw as little as 20-50mA @ 5V. If you are already using the power bank to charge a device such as a mobile phone, you won't lose much power by plugging the low power light into the power bank at the same time to get some useable light for the table too (this assumes you have a power bank with 2+ USB outlets).
The high power ones tend to be a small plug-only lamp without a cable and sometimes get quite hot, perhaps also heating up the power bank. If you get a long USB extension cord, you can suspend it like a pendant light providing area lighting and keeping the heat away from the power source.
