. Can be, I have made a misstake - as Webber1 said - and I didn't leave it burn in.
Burn in time from the practice seems to depend on the voltage of the device (Burson works in the range 3.5V-16.5V) so it can take shorter or longer. On my Asus STX II it took whole month (600 hours) due to 5v voltage, and on Hegel HD12 it took about 200 hours as it works on higher voltage.