You may already know your battery is best served by shallow discharges, but calibrating your battery occasionally is important too. If you don't, the display that shows you how much charge is remaining can be wildly inaccurate.
Photo by Kyle Van Horn.
If you've ever seen your battery zoom from half-full to near empty in what seems like an instant, or plugged in your charger and then unplugged it only to see what you thought was 100% is really only 90%, your phone or laptop battery may not be properly calibrated. Over at How-To Geek, Chris Hoffman explains that regular top-offs are important, but a good calibration is important too:
No matter how well you take care of the battery, its capacity will still decrease as a result of unavoidable factors like typical usage, age, and heat. If the battery isn't allowed to run from 100% down to 0% occasionally, the battery's power meter won't know how much juice is actually in the battery. Manufacturers generally recommend calibrating the battery every 2-3 months. This helps keep your battery readings accurate.
In reality, you likely don't have to do this that often if you're not too worried about your laptop's battery readings being completely precise. However, if you don't calibrate your battery regularly, you may eventually find your laptop suddenly dying on you when you're using it -- without any prior warnings. When this happens, it's definitely time to calibrate the battery.
We'd suggest making it part of your regular PC cleaning ritual. Calibrating your laptop battery isn't hard -- it's essentially the process of running your battery down to near-empty and then charging it all the way back up to full.
Some PC manufacturers have utilities that will do this for you. If you'd prefer to do it manually, the full post linked below will explain how to do it. (Note: If you own a Macbook made in the past few years, Apple says you don't need to worry about calibration at all, as OS X handles it for you.)
If you're interested in calibrating your phone battery, things get a little trickier. There are apps that can help (note that most Android apps require root to keep the phone from just powering off while you're calibrating). You can always take a manual approach and leave the phone discharged as long as possible, then plug it back in until it's fully charged. This StackExchange question may help Android users, and this article at MacBlend should help iOS users.