I've only has this shade sail up since early July....so I'd say the tabs holding the D-rings in place only last a month.  Three weeks ago, one of them ripped loose, not frayed, it looks cleanly cut through.  There's no way to re-attach it so I had to punch a hole and insert one of those big metal eyelet rings you put through canvas.  It worked well.  3 days after putting it back up...ALL 3 of the other D-rings ripped away, granted it was a strong storm that we had.  I'll do the same to fix it.  But it's safe to say that this is a 'fair weather' shade only.  The metal rings that I'll have repaired it with are going to hold it better.  The original D-ring system on it is poorly done.