Have just checked the stay alive on my lovely white cabbed 'Tulyar'. With all CVs set to out of the box values, I can confirm that stay alive works for around 3 to 4 seconds with sound and lights on after lifting her off the track. I'm using my home-brew DCC++ controller with JMRI throttle.
Interestingly, previously I had unknowingly been testing my locos with the DCC++ power supply set to 9V!
As a rule I set the PSU to 15V (to the DCC++ Controller) for OO. I'm somewhat surprised that the decoder worked at all on the lower voltage.
(Just to be clear, the 3-4 second stay alive time test was carried out with the controller's power input set to 15V)