The use SMART (Self-Monitoring, Analysis and Reporting Technology) is brilliant in concept, but in practice it has not proved as useful as it should. Using the statistics and other data provided by SMART, it should be possible to predict when a hard disk drive is about to die. However, there are many different values returned, with no consistency even from drives manufactured by the same disk manufacturer.
Many of the values have little or no significance in determining the impending end of life for a disk drive. Error rates and temperature fluctuations are however probably the most important factors which may indicate a problem is impending. If the hard disks are running hotter than normal, anything above 40 degrees Celsius being a potential problem, may indicate insufficient cooling, which should be addressed, otherwise any replacement drives may also operate at high temperatures.
The error rates are likely indicators of an impending problem with the drive, but in themselves are unable to predict the remaining usable lifetime of the drive. Should these appear it is essential that any data on the drive which has not already been backed up is secured before the problem becomes terminal.
Many computer users turn SMART off, assuming it is of no use, while others do not even know that this diagnostic information is available. There are many tools, but often the information is not presented in a fashion which makes the data of any use unless you have an in-depth knowledge what the values represent.