@moofang

i've been charging my phones at night since the brick phone days. i wouldn't say it would make a significant impact with your battery. if your really worried, set your alarm to wake up after 2 hours and unplug it
or email nokia support with the question of does the n9 have this trickle charge feature like the n900" could explain why some people are saying their phone only show's 97% charged after it says it's fully charged.