2015-08-08: Request from comments below: Added description why I am using a timer switch at all.
Many smartphone owners seems to live with a constant fear that their smartphone might die. A clear sign that you might be affected as well could be that you find yourself in a situation where you desperately need to charge your phone during the day.
My personal approach solved this issue for me once and for all: Close to my bed, I have a time switch installed. A dual-USB-charger is plugged in. The two cables are mounted along the bedsides and reside on/in the nightstand.
Whenever I go to bed, I plug in the phone after I shut it down. From 2a.m. to 5a.m. the USB cables get power from the time switch. Whatever battery status my phone had, I get a hundred percent battery capacity in the morning when I turn on the phone. Since my smartphone is able to deal with all kind of stuff for at least one day, I never ever have to think about the battery again. One thing less to worry about.
Of course, there are exceptions: For example whenever I travel, I do have to take a charger with me and I do have to think about charging again.
The purpose of the timer switch is that I want to define the charging hours. This way, I don't over-charge the battery for sure. This might not be an issue at all for modern smart phone batteries and their advanced charging logic. However, when I re-charge the battery every night, I don't want to take chances. Further more: I don't want to be annoyed by the LED that is on when the phone gets charged. By the time the timer switch turns on, I am already asleep. And it saves (a bit) power.
A remark on technical progress: Before smartphones were introduced, we had phones and PDAs with batteries that lasted for weeks.