Have an 2 Blue ray writters; an LG (E6400 Vista 32) and a Pioneer BDR-205 (Win 7 64). Like you I verified that I could write when I first installed then and have since just used them for writing to DVDs and occassionally playing a Blu-ray.
When I was transferring an number of my DVDs to a Backup dvd I use to verify the write quality (Used Plextools with my Plextor DVD drive, and used Nero CDSpeed with A Samsung looking at PIE and PIO errors. MEDIA and write speed max a big diff. For my DVDs I still only use 8x (on 16X media) if I plan on keeping. NOT sure (Have not looked) to see if Blu-ray can be checked. In your case I think you will find a large number of PIE error, If true then that would explain - The higher the error rate the shorter the life span.
Could also be the Media (Error checking whould show this), might try decreasing the write speed, Even if the drive says 12 x ok even thoght media is not rated at 12 x does not mean no sweat - it may be a good burn and again it may not.
Be sure not to use the Verbatim 2x LTH media. This LTH type of media is less expensive, but is based on an organic dye material and has a higher sensitivity to light and therefore will have less compatibility and shorter life span.