I have had two "tension shackles" fail (so far!). Both saddles were date code 1707, honey.
One snapped after 618miles, returned to Spa at my cost (they did not refund the postage) for a very slow trip round the world on a long holiday, not yet been re fitted to a bike.
Second snapped after 2616 miles. E-mailed Spa asking if they had parts available rather than posting it around the planet. No response.
Both failures were on a fixed track bike I used for commutting and audax with carradice bagman bracket.
Ordered a Brooks BYB140 from SJS (chrome version, Ti version BYB289 out of stock and bloody expensive), which fitted after a little fettling with a file to trim the nose height.
One other on a bike at the moment, 1624 miles date code 1610 in black (geared bike used for audax, also with bagman bracket).
One other unused waiting for me to get round to fitting, date code 1610 in brown.
I have another BYB140 in the spares box, it's easier to fit than it is to change a saddle.