As a chemist, I can educate you a little on Li-Ion battery charging.
If you start out with a car that has just been washed and is clean ... then spray water on it and let the water dry, you will notice water spots. On one side of the car, wipe off the water spots with a damp towel. Now put the car in a garage and wait a whole month or two before wiping off the water spots on the other side. When you go to wipe off the water spots on the second side, it is MUCH more difficult to get the water spots off. The same concept applies to a battery. A battery has metal ions in solution that plate out onto a cathode (think of salt in a glass of water), and in this process, electricity is generated. When you recharge the battery, the reverse process occurs. Now here's what applies to charging and discharging ... if you don't run the battery all the way down for 30 days, a bunch of the ions in the battery become stuck (like the water spots) and may not move into solution again (loss of battery capacity). The same concept applies to charging the battery all the way up. There are two ends (empty and full), and you need to get both ends into solution (complete discharge and complete charge) to prevent the ions from sticking and loss of battery capacity. You don't have to be obsessive though and go through a complete discharge-charge cycle every day or every few days. Apple's website advises that you run your battery all the way down and charge it all the way up at least once a month. My advice would be at least once every two weeks. Aside from that, charge and discharge however you want - it won't make a difference. When you first bought your phone, they told you to completely discharge and completely charge the battery ... that's because the phone was probably sitting on a warehouse shelf for two weeks or more.
