Is Battery Calibration important?

Never drain the battery to 0. Some batteries may not recover and cannot be recharged. Practice staying between 10-20% then recharging.

About Batteries in iDevices

1. Apple - Batteries
2. Battery University
3. Apple - Batteries - iPod
4. Apple - Batteries - iPhone
5. Apple - Batteries - iPad

Not at all. This User Tip may help:

When to charge your iPhone or iPad

That has not been required nor recommended by Apple for several years.

And note that the procedure never did anything for the actually battery itself. All it ever did was calibrate the software that displays the battery level icon in the top right of the display.

Deep discharges are actually not optimal for any lithium battery and accelerate normal aging and degradation.

Hey Kappy I wanted to let you know (if you don't already) that number 3, 4, and 5 are different links, but all three lead to the same website. 😕 😕

Good catch, Gus.