Can I leave it plugged in for charge all the time? -Samsung Galaxy 3 I5801 In short my question is -
What is the battery level at which it starts charging again Samsung Galaxy 3 I5801 device when kept plugged in for charge all the time?

If you want to know background and why I ask this, read whole question below.

This question is based on below answer 
Do I have to charge my phone before I use it the first time? 


  Can I leave it plugged in all the
  time? Yes, and no. This is very
  dependent on whom makes your device.
  For example, my Lenovo laptop will not
  apply a charge to the battery unless
  it is under 97%. When it does charge
  the battery it charges directly to
  100%, then stops until the battery
  sags below 97%. Many laptops did not
  do this, on most just applying charge
  if it is not 100%. This would put the
  battery through thousands of charge
  cycles in a week when you are not
  using the battery. This ages a battery
  quickly.
  
  If your phone maker took the time and
  paid the extra cash then your phone
  will stop charging once it reaches
  full charge and just power the system
  from the wall outlet. It is
  significantly more likely that your
  phone is charging your battery on a
  short cycle and aging it thoroughly.


The answerer mentions that it depends on manufacturer. What's the answer for Android phone? Or if it depends on the Manufacturer what is the battery level at which it starts charging again Samsung Galaxy 3 I5801 device?

So this question is specific to the device - Samsung Galaxy 3 I5801.
I don't know about your specific device/battery but here is a rather detailed article on the battery in android phones and the app used in the article to log battery information is called CurrentWidget

If the article is representative of most smart phones, which I suspect it is, to maximize your battery life your phone does an initial charge to 100% and then maintains the battery at about 93%.

My takeaway is that it is good to leave your phone plugged in and charging when you can but it is not good to frequently plug and unplug your phone.