First of all, the comparation with consumer-grade products is flawed: consumers want the most complex systems at the best prices; that gives little room for manufacturers to provide ruggedized, durable hardware $^1$. The exception would be with vehicles, but those are subject to heavier workloads.
Second, intent. Even if a civilization is very advanced, making hardware that lasts so long without maintenance is a effort that needs to be justified. They would need to have a reason to design hardware that way. In other words, I would not expect everything from such a civilization to be still working after hundreds of years; only items designed and stored for that purpose. For example, the office kitchen will not work, but the bunch of robots that were being prepared and packed for a transtellar expedition could have survived.
As to how it could be achieved, two ways:
* Some items could be packaged/sealed off to maximize their endurance (powered down, no oxidizers)
* Robotic maintenance. Of course, this will mean that the system would need the ability to repair and ever recycle robots. 159
Also, it requires a functional power supply.
* A mix of both (robotic maintenance of a small core that is always active, packaged hardware ready to be activated).
As for the energy issue, two ways:
* For "packaged" units, thermoelectric nuclear. Store radiactive materials with long half-lifes isolated one from the others. When you activate the unit, put those materials in the power unit of the hardware. The increased amount of radiactive nuclear would increase the rate of nuclear desintegration, increasing the power output (try to avoid a runaway chain reaction, though).
* For robotic-maintained systems, you can use nuclear fussion. The combustible (let's say Hidrogen $^2$) does not decay, so you could just have a BIG tank of it and just spend it little by little. Additionally, you could filter it off from the environment.
$^1$ Would you buy nowadays a Nokia 6110 for US$200, even if it was guaranteed to work for 50 years?
$^2$ We would have issues storing Hidrogen for so long because it leaks, but maybe an advanced technology would not have such issue. Or you can use other elements like Helium. 435