WD MBLD time machine backup problems

I am running 10.8.2 on my Mac and using time machine to backup my data. I am now on my 3rd WD drive after failures on my first 2. When I received my latest drive the initial seeding was ok, took a long time but there was quite a lot of data. Since then the backups either dont finish (over 24 hours and still running for 10 GB) or take absolutely ages.

Anyone any ideas as I am getting totally fed up with these drives now and my experience is not good. Backing up to another external drive I have (WD as well) works fine and is quick. I have all of the latest firmware on the WD MBLD.

You might to contact apple first regarding this issue. If you can copy and paste a file to the drive, it means the drive is working.