Source: I have a master's degree in mechanical engineering in hybrid vehicle powertrains, and a big part of my research was battery technology. I spent some time working with the folks at National Semiconductor learning this, so I have several primary sources.

Disclaimer: my knowledge of the field is from ca 2010.

1) Lots of deep discharge cycles do negatively affect battery life. Try not to jump between 0% and 100% too much.

2) Li-ion batteries do not love being at 100% SOC (state of charge). As batteries become more dense, the membranes become thinner. High SOC equates to high chemical potential, which will break down membranes faster. As such, avoid leaving your battery at 100%. This wasn't as much of a problem with older batteries with thicker membranes, but is becoming more and more an issue as we try to squeeze every ounce of density out of batteries.

3) Roughly 70% SOC is where a battery is happiest, but the whole range of ~30-80% is pretty happy for a li ion cell. Try to keep your battery at ~70% or so overnight, at 50% or so for long sleeps.

A good usage pattern: plug in and let charge to 90%, unplug and use for a couple of hours, plug back in at 50% or so, rinse and repeat.