The average lifespan of computer/laptop, without replacement, upgrade, or addition of hardware components from the original configuration, depends on several factors; the components of hardware, operation system & the applications to used (needed), and frequency of use.
If it depends on hardware components only, there are still other factors that influence it; frequency of use. Is it is rarely used it can be 15 years old, if it is often used (especially for playing games) it is around 4 or 5 years, and if it is not used too often then the average age is 7 to 8 years.
Nonetheless, taking into account other factors of need at this time (storage capacity requirements, replacement of operation systems or certain application including browser, zoom, graphic editing, video editing, game, and the like), which has the consequences of adding or replacing RAM, hard disk/SSD, and processor, then the age of laptop/computer (which don't change configuration) is around 3 or 4 years.