Should I shut-down my GS3 to charge?

[Szadzik]

It's for this reason I usually don't charge overnight, and I generally don't leave the charger plugged in for an extended period once fully charged.

I typically go to bed w/enough battery life to make it through the night. I'll charge it in the early evening, if necessary.

You will be keeping the phone for at least 5 years I assume? If not, charging every night only means 730 charges in two years, while batteries are usually specced for 1000 charges and 10% loss of capacity in that time.

There are other dimensions to this question. One is long term battery life. If kept between approximately 35% and 75% charge (this equates to a specific minimum and maximum voltage) the kind of Lithium Ion cells used on mobile devices can be charged and discharged 2000-3000 times. If charge cycles routinely go to 100% and down to 15% or less, the useful cycle life drops to around 400. If charging your device when you hit 30-35% and stopping when you reach 70-75% is too cumbersome for your schedule, you might at least want to alter your habit of keeping the device at 100%. The more time a Lithium Ion battery spends at full charge (4.2 volts), the shorter the total cycle count. This high voltage stresses and deteriorates the cells rapidly. This is only a snapshot of a much larger picture but it may be useful to a few of you.

As for charging with the phone on or off, one consideration is the rate of charge. Other things being equal, the slower the charge, the less heat build-up in the cells, and the longer the cell life. If leaving your phone on results in a slower charge, and you have the time, you will benefit in terms of long-term battery life. However, some chargers have the surplus capacity to charge your battery at the full rate and run your device at the same time. If so, it won't make any difference.

This is all true, but the impact is too low to care.

simple answer to the question....no, not necessary

Exactly.

The only trick I have for charging overnight is using a low current charger. Instead of the factory one, I use a 500mA one and that is it.