Have you not asked yourself....
" If the blades will last 12 years and time-out, why have Robinson issued an AD and giving a 50% trade-in allowance ?
I would suggest, you will have had 8 years ,come June 2016 -so, that's 66% of timed life....In effect, Robbie are giving you 16% extra time , free, and, more importantly, hopefully selling you a safer blade.
There has to be a damned good reason why they have issurd an AD....the blades are unsafe?and a damned good reason why they are giving you an incentive to buy some "new, improved, better-quality, safer blades"
If you can afford to run the machine and if you value your own unexpired life, reduce the risk and change the damned things NOW !!!!