They are useful for three years. A life span that is longer than a paper towel but shorter than a chair. A school technology plan must recognize this by detailing the means of replacement. Maintenance must also be planned for. A school is in the business of education not computer repair so a three year full warranty should be purchased for each new computer.
Software has an even shorter life span than hardware, about two years.
A school technology plan must recognize the replacement costs of all software, operating systems, utilities, productivity suites, and applications. Never buy closeout or discontinued software with no user support. Integration will not take place without continual publisher support.