What model of samsung was it? The v series or sp series or something older? The SPs are very reliable. Even the v30/40 drives are pretty reliable.

7200rpm drives generally require active cooling to last long. A small front case fan is good enough. I did notice that my 250gb samsung runs relatively cool even without active cooling, but its not something I'd recommend.

And about warning signs, check the smart status using everest or something. I'm very sure samsung drives give plenty of notice. By the time you get to whinny noises and bad data, its ready to explode.