Yeah I have heard of this. I recently contacted a few people at DFR (my case manager included..) to ask about the validity of my test, and they also told me 3 years. To be honest I don't think what they have to say holds much weight. No one seems to have much interest in the finer details of the applictaion process for pilots, or any other career path for that matter. I always thought that the pilot spec testing had a 1 year 'use by' date, regardless of performance. Nonetheless it's probably best to aim to get your assesement day out of the way before a year passes...