There isn't an exact answer to this, all drives have a chance of failing. The best you will likely get is a few peoples experiences with different drives which aren't really that telling.
Go with the drive with the best warranty at the best price point and realize the drive may fail just like any other drive might. Keeping it in one location and never moving it will definitely help keep it from failing, but that certainly doesn't mean it still can't.
thanks for your advice between the WD My Book Live and the Seagate Free Agent is there one that you would choose ?
once again, thanks a lot