I've seen some forumites say that theoretically electronics should last for ever because there are no moving parts.
But that is not true.
At a microscropic level, electronics systems go through
huge physical movements which can be very destructive!
What moves them? Not the electrons, which are of course quantum entities.
Countless studies - including a landmark one by US Dept of Defense - have shown that, direct external physical damage aside, about 80% of all electronics failures are caused by thermal issues.
In other words, Heat is The Great Enemy.
There is plenty of reference material on this topic, easily
soopled. Even
Miss Dewey can help. Or consult your fave search provider.
Perhaps the most common destroyer of electronics and especially electro-mechanical components (such as HDDs) is thermal cycling. This is the successive heat-expansions and cooling-contractions that a connection or component goes through whenever you power your system on and off, ie take it from cold to hot to cold. A typical PC has tens of thousands of micro-connections at board and component level, often between materials with different thermal and expansion coefficients. Passing current through the system causes each connection and each component to heat up and expand. When you power off, they cool down and contract, each material at its own rate. Successive thermal cycles slowly but inexorably strain the weaker connections, driving them closer to inevitable failure.
That's why almost all failures take place during the power-on or just after the power-off cycle (the system won't restart).
It's also why many devices have 'standby' modes ... such as your TV, for example. The main aim is to keep the circuits hot and reduce/stop thermal cycling. But hibernation or even standby mode on the PC stops current flow and allows the system to cool down.
This is especially true for devices like Hard Disk Drives. The MTBF figures published by manufacturers assume constant running at constant temps. Small example of just one item: every time your hard drive powers up the tiny bearings (not just of spinning disk spindle, but also of actuator r/w arm) take huge strain because they're not yet at the operating spec tolerances (which assume expansions to optimal operating temp). The lubricants are also designed to run optimally at normal operating temp, and are largely ineffective when a cold start is commenced. Zillions of micro connections and hundreds of solder joints and connections also take huge strain during these expansion and contraction cycles.
That's why, someday, something in your PC just stops working.
On my one server I have several hard drives that have run virtually non-stop for 8 years. The drives are far too small now, but when I replace the system next year I'll expect the same lifespan because I keep thermal cycling to an absolute minimum.
