Every 4-5 yearsLong answer:
Choosing when to replace your computer is based on 6 reasons.
Most users compare depreciation of computers to their cars, and that's just plain wrong. Cars generally go from A to B and depreciate by mileage and years. That's it! Computers are very different from cars. This is because computers are part of an ecosystem that is constantly changing around us. For example, if you bought a new printer and attempted to install it on a computer that was brand new but unused for 8 years (true story), then there is a high chance your printer won't even install. This is because the printer software wants you to update the computer to support the printer properly. These updates would have occurred regularly over the past 8 years, which would have allowed a smooth installation. So unlike a car, where it could be sitting for years and not actually become useless, a computer can start to lose its capabilities. If you were to bring computer depreciation to car depreciation, it's like driving a car under constant changing roads, construction sites, bumps, and other things that never
stay the same over time. Imagine your commute home from work always being different. Sometimes you're driving downhill, and other times you're driving uphill over bumps and gravel for several miles. Your computer will always require some form of update or upgrade, which makes it ever-changing. This makes the depreciation of a computer closer to the expiration date of batteries than the long term mechanical stability of a car. Most computers, will depreciate significantly after 4-5 years constant change due to their ecosystem.
2. Performance and features
Today's computers, just like tomorrow's will always be faster than yesterday's. However, computers that are more than 5 years old are much slower than today's computers. This is due to the frequent change in processor, motherboard, and memory technology. Instead of having a processor with a single core (think brain of computer), today's computers can have at least 2 or more. This is a 100% or more increase, paired with faster memory and higher speed transfers which allows us to watch HD videos, enjoy more rich content from websites and programs, and play newer type of games.