Try 56 years and counting.
That makes some sense. At this stage, Grant still hasn’t been confirmed as THE guy for the job, so maybe all SPECTRE assassins train this way, to reinforce the mental conditioning: “If you ever see this face, kill, kill, KILL!”
However, if they’re this good at making Bond masks, why not just film that incriminating sex scene with Tania using an imposter? Then they could make it as kinky and incriminating as possible.