I have seen the message numerous times and it stinks that it lasts all of 2 secs...but that is just to alert you that a regen has started....it will continue until it finishes like Thom12 says in roughly 10 minutes. And here is the stupid part - there is no indication when it finishes!

Of course if you shut the vehicle off during the regen and it is not complete it will try to finish the next time engine temps get back up to normal, about the time I am pulling into work or the driveway.

I have tried to watch the instant MPG to determine if it has finished or not and sometimes (during an active regen) you can let of the accelerator and see that the mpg does not go up, which indicates it is doing the regen. If it is doing a passive regen (and this is where I am totally unsure what the hell this is ) forget using the instant mpg as an indicator of anything....:-