Well, there is a grain of truth in what's been said, in that older Li batteries didn't mind charges that were < 3% or so, as they never counted as a cycle. Note that topping 3% is NOT trickle charging.

Newer chemistries do get bothered by small charges so Nokia has to choose between protecting the battery and letting you leave home with a low battery. They chose 80% and frankly it's fine. Could be 90, but in time battery will lose capacity and when "top" is 92%, it will destroy it cycling it 4 times a night. Also, if you leave it charging and doing something, it could cycle like 20 times overnight.

80 is good, leave it be. If you want to make sure it's full, leave it charging until LED is green. It's full then.

Also, battery charges faster from low to medium than from medium to full, as above some 70% or so the rate drops (Assuming Nokia can charge a battery right, and they do). So top charge at 40% while at work rather than overfilling it to 99.9 at home. 20 minutes in a charger will do wonders. Use a wall wart.

Last but not least, a little rant. Please, before starting a hints and tips page, make sure you check your facts. Ask around. Battery university has a must read.