The method of draining the battery on an infrequent basis was a spill-over from the Nickel Cadmium battery days (more than a decade ago), and to a lesser-extent Nickel Metal Hydride. Those batteries had a characteristic whereby if you used it for only a portion of its full charge on a regular basis, eventually the battery would "assume" that amount of charge consumed as its full capacity.
For instance, let's say you used an average of 60% of the battery's capacity, so you charge to 100% overnight, then use to 40%, then repeat, and you do that for several months. What would happen is the battery's internal chemistry would essentially build up crystals (Dendrites) that occupied the space originally occupied by the Cadmium paste which allowed charge to happen, essentially blocking that portion of the battery's physical space from being active and able to maintain a charge. So eventually even if it was fully charged, it would start dying at 40%, rather than continuing to provide power to 0% as expected. By repeated deep-discharges followed by repeated full charges, the battery would reclaim some of that space by breaking down the Dendrites. This worked - somewhat.
Eventually, there was a system developed by Cadex (the parent of BatteryUniversity.com), which would "zap" the batteries with a series of quick high voltage jolts that helped to break up those dendrites and reclaim more of the battery's charge capacity (see
Battery charger and battery analyzer experts - Cadex Electronics Inc.). I still have the one I purchased back in the 90s, and used to keep my Motorola Flip Phone batteries going strong. By using this technique, they could reclaim upwards of 90% or more of the original capacity and revive batteries that would have otherwise been thrown away and replaced. The savings for fleet management (such as Police, Fire, Ambulance, Security, etc.) was tremendous. The term coined by Cadex was "Battery Conditioning". This has led to the same terms and deep discharging techniques being incorrectly applied to "other" battery chemistry. This is totally effective ONLY with Nickel Cadmium batteries and should NOT be applied to ANY other battery chemistry.
Today there are "Universal Battery Conditioners and Chargers" which are intelligent and can detect the type of battery being tested and charged, and will change the charging algorithm to fit the particular battery chemistry. Since some batteries (namely Lithium based batteries) can't be continually charged or they will rupture violently, these universal chargers are equipped to shut off charging when the battery has reached its optimum charge, then monitor it to assure full charge and "top off" as necessary while on stand-by. For us, our phones have a similar version of the same smart battery charging technology built it, so as long as you use the phone and the original charger supplied by Motorola, you'll never have to fear a problem.