so i just backed up everything onto one drive (lacie golden disk 500gb). i just read about hard drives dieing and losing info. this is stuff i cannot lose and have worked on for about 10 years. if i just kept this external on a shelf and rarely used it...how long can i expect it to last. i took everything off my maxtor (250), western digital 250, and western digital passport 160. selling the maxtor and passport. how often should i update externals?