if you leave lots of data on there, be sure to exercicse the drive about once a week or so. (ie. spin it up, access a few files, etc). Only takes a minute and will extend the life of your drive.
fwiw, we have about 100 external 200gig drives down here with archives for BMG and Universal. We exercise them and everything is stored in triplicate. we have not had one drive failure in 1.5 years.
h