Tried this last Dec and it worked --passed an Etest 2 days after my birthday in Dec 2008 for a 92 S13 -so that e test is good until 2 days after my birthday 2009 -just received the renewal form and I get 2 more years out of that etest until Dec 2011 so essentially 3 years in total 
This would not have worked on an odd # year car in 2008 but would in 2009
Nice lol - Etest is due Jan 10th, 2011 on my jeep, my birthday is jan 6th, so I’m hoping the same happens for me (i.e. jan 2013 :D)
stick it to the man…