I had passed 5 of the 7 ATPL's for helicopter (self studied), and due to personal circumstance I didn't have the chance to finish the last two within the 3 years.
I did the whole lot again (much easier the second time around, albeit even more painful to shell over the $$ for exams you've already passed), also self studied.
I say suck it up. The only legitimate reason I could see is if you were sitting your last exam (with only a few days left for the 3 years to lapse) and the ASL computers crashed etc.. Maybe that would warrant an extension to an immediate re-test when they're back online.
In essence, I also think that no-one should get an extension. It's your own fault for not finding the time to finish the exams within the alloted timeframe.