No what you are doing is harming the battery life. Those rules you are using are for older battery types. You should always top off. And charge whenever you can for best battery health.
Charging your iPhone overnight will not harm your battery in the slightest.
You simply can't overcharge an iPhone, or any other modern electronic device, for that matter. Any device that uses a Lithium Ion or Lithium Polymer battery must incorporate a charging circuit that cuts off charging power when the battery reaches 100%.
In other words, when your iPhone is plugged in and reaches 100%, it switches to external power and simply runs from that.
Similarly, charging your battery before it's fully depleted will also not harm your battery at all, and is actually the preferable way of charging your battery. While Lithium Ion batteries are rated for a limited number of "charge cycles' (about 500 in the case of the iPhone), the term "charge cycle" refers to complete recharges, and partial recharges simply use up partial charge cycles. In other words, every time you charge your iPhone up from 90%, you're using 1/10th, or 10%, of a complete charge cycle. This means you could charge your iPhone up from 90%-100% 5,000 times before you'd have to worry about running out of charge cycles.
However, if you deliberately drain your battery to zero and then recharge it, instead of simply plugging it in when it needs to be charged, you're needlessly using up a complete charge cycle. Obviously if you're using your iPhone until the battery goes dead, that's fair, but there's no need to deliberately drain it before recharging it, and you'll actually shorten your battery life if you do so.
The bottom line is that most people worry about their batteries way more than they need to, largely because of very real issues with older Nickel-Cadmium (NiCad) batteries that no longer apply with Lithium-Ion batteries yet remain persistent myths that refuse to die. For the vast majority of iPhone users, you're safe to plug your iPhone in when you need to, leave it plugged in as necessary, and use it normally. You're not hurting your battery by doing so unless you're a seriously atypical user.