Hello Tan
Yes, the system should work the way you defined above. The depreciation should end in Nov 2012. When was the negative values to the asset posted? Please check if some one changed the depreciation key on the asset? Also what is the period control that you have for the key?
If you have the settings like below, then your Dep Key is correctly maintained.
Multi Level Method: Base val = 01, Rem. life indicator should not be checked
Period control = Period start date
Base Method = 0007, Dep Method = D
If you have the above settings, then your config is correct. In that case I would guess some one has changed the master data.
Thanks
Asheesh Bhatia