Instruction: Answer the given question by extracting information from the supporting document.

Input:
Question: Can I just keep it plugged in with the batteries until needed, or do I need to unplug it once the batteries are fully charged?
Document: I searched around for awhile to find a charger as simple and compact as the Apple one, but honestly at $28 I think it&#8217;s worth it to get a charger you won&#8217;t mind having out somewhere convenient instead of trying to hide it away. Plus it comes with 6 batteries, which should be enough for your mouse, keyboard, and 2 spares to keep charging until needed.If you need more batteries I definitely suggest Eneloop[...]
Bought this to always have charged batteries for the office. Always have one set of batteries on reserve and fully charged when a Mighty Mouse has burnt through it's batteries.Highly recommended if you have more than 2 sets of batteries that need recharging.
I needed to get this because it seemed a good way to not buy a million AA batteries. I use this for my wireless mouse and keyboards. So far, after the initial short charge the batteries keep a charge real nicely. The first time I probably didn't charge them long enough (impatient to use) and the mouse batteries charge only lasted about two weeks. After that with a proper charge the mouse batteries are still at 60% after a month.
I have a wireless mouse and keyboard. It seemed like I never had the batteries I needed. With these rechargeable batteries I always have the batteries I need.
For some reason, I thought this charger would charge 4 batteries at a time, like my old one. It only charges 2, but they seem to hold charges much better than anything else I've used. And I can leave it plugged in until I need to replace the batteries in my mouse, keyboard or camera.
The charger works great and is easy to keep handy for when you need the batteries for your wireless mouse or trackpad.
The design is elegant and concise. Note that the batteries are not fully charged when they come. It works well when I charged the batteries.
It is a small little box containing the six batteries and the charger. They come fully charged. I am using in the magic mouse for some weeks and they didn't discharge.
Comes with six batteries which gives me a spare set for when the mouse or keyboard reports a low battery warning. These batteries hold their charge for quite a while even if they aren't being used, so I tend to charge the low ones as soon as I remove them from the keyboard or mouse and then just set them aside for 30-60 days in a fully charged state.
The batteries according to my computer were charged only at 76%, odd for saying that it was fully charged. So placed them back for another 2 hours until it was green again. The batteries were still at low charger around 80%, I don't know why exactly the batteries just don't fully charge. Currently it has been about 4 days without using my keyboard and they are staying strong at around 60% battery life.
Answer: I don't leave mine plugged in and I found this on the Apple forum.."Thanks to an intelligent power management system, the Apple Battery Charger uses less power once your batteries are fully charged, making it one of the most energy-efficient rechargeable battery solutions ever." However, for maximum life, you should not leave the batteries plugged in all the time." It doesn't take long for the batteries to charge fully and if you have an extra set charge them as soon as the "mouse batteries low" shows up on your screen and you should have no lag time.