I read Maurice's latest post over on film tech and thought I'd share my own experiences with such devices.

Whether it be numerous vape batteries I have used over recent times,an led torch with rechargeable batteries, a laptop, tablet or phone,.. all devices I simply just charge overnight with no set time factor to them.

The only device I have had that even warned me not to charge beyond "the green light" was a few of the De Walt power tools that I have.

I don't think in most cases it matters how long, just that they are in need of charging in the first place by beginning charging from empty, to maximize capacity from their batteries at all times.

Thanks for your input, Andrew, my USB light is fully charged as received.
My digital camera has a charger for its battery. Light indication shows when it is fully charged and ready to go back in the camera.
But this great little torch is a different matter. I have no separate charger, so it's either my computer, or the car. But these have no charge indication.
So, as one helpful person said, "just leave it overnight".

I was given some unofficial advice by a US employee at Dell (something which isn't revealed in their own product details) that the way to prolong battery life on their laptops/tablets, is to charge to about 90%, and only let a device drain to about 10%. In many cases, this isn't practical, because we'd have to do most charging during the day when we're using them. I can't make this system work with my phone, but I pretty much always use this method with my hybrid tablet/desktop setup.

Yes Maurice, more sophisticated products as you say, like my own digital camera and power tools etc etc, do indicate when fully charged.
Even relatively inexpensive items such as my vape batteries also have an LCD display which indicates when the batteries are fully charged.

There are however, many other devices made now that simply supply you only with a USB lead for them which as you say, can connect to your computer or car USB or cigarette lighter port etc etc, that have no indication of their remaining power level.

I don't think you can ever do it any harm to it charging it overnight but my advice would be to charge it during your waking hours from your pc if it makes you feel safer in your home.
Some unscrupulous counterfeit devices deriving from China, have been known to set on fire due to poor manufacturing standards and cheap components used in them without the necessary safety devices also fitted.
Even some fairly expensive ones like a certain range of Samsung phones I can instantly think of have also suffered from potentially hazardous power supplies to the units so I'd say, unless you are entirely certain it is manufactured to European safety standards and regulations, I'd err on the side of caution and perhaps charge it during the daytime where you can your eye on it, certainly until your confidence is sufficiently earned at any rate.

The torch has no indication of manufacturing country. All it says is "USB input: 5V".
Perhaps it's best to connect to my computer as I compose things to type. I can then keep an eye on it.

I agree Maurice.
I am certain everything will be fine with it though.
Still,. better to be safe than sorry as they say, especially while anything is new to the home.

I read that most computer USB ports can give 500mA max output and provide 5 volts x 0.05A = 2.5 watts.
The Amazon ad for the torch says it has an 600mAh lithium battery.
My memory of electronics indicates that it should take a full charge in just over one hour.
Am I right?

500 milli amps is half an amp Maurice (0.5), not 5 hundredths of an amp or one twentieth of an ampere. (0.05)