i've had a 100G Hitachi that i extracted from a laptop made in 2006, and it's been my Win7x64Pro OS drive for years, and a previous OS before that. worked perfectly if a bit slow (eh, 2.5" drives are usually 5400rpm anyways, except for WD Black). still works perfectly as an external drive in a portable case. so, it's what, 7 years old? never had any issues with it. S.M.A.R.T. data scans show it to be in better shape than a younger Seagate 3.5" drive, so... read into that whatever you like.
eventually, all drives either succumb to failure or irrelevance (by just being too darned small and it being cheap to buy a new one 10X larger)