Ah... we are talking about lithium battery abuse! And you have to be careful with all of the information out there, as some of it is wrong. Like the memory effect of Ni-CAD batteries has a problem with capacity if you didn't discharge them down to say 0.9v per cell and then recharge them full once again. Other battery types including lithium batteries, doesn't have this problem. So the practice of discharge and charging cycles are a waste of time.
And no, it isn't bad to use a battery down to 30% and then recharge it. Nor is it bad to take a partially charged battery and use it. But don't do the following:
- Charge while frozen (they can explode)
- Charge when battery is over 110 degrees F (their lifespan shortens a lot)
- Charge higher than 4.20v per cell (for 3.7v lithiums, as they can explode)