I have 5 PS2s. 4 slims and 1 phat. Phat i just clean it and dust it. Early models were unreliable.
Slims I've replaced the spindles and 2 of the lasers.
Mostly the spindles plastic disc holder tab would break. Other than that, just general cleaning maintenance and even running mod chips it's been ok.
Also, as mentioned above some ps2 earlier models do run a bit hot. I've modded a few by making vents on the top of the case above the heatsink for heat to rise out.
Ps2 controllers the OEM Model H i think have a higher failure rate. The circuit board shorts out or something.
Original xbox; I own 4. Only 2 of mine came with clock capacitors and those I removed. All have had at least 2-4 big power capacitors replaced as they were starting to bulge out. Every xbox i've opened has had at least 2 power capacitors on the motherboard bulging.
Disc loader about 1 in 3 needed the rubber dvd drive belt replaced.
Original xbox controllers; squeaky triggers, adding lithium grease makes that go away.
A lot of the controllers I always have to take apart as that flex section on the cord from the controllers, always frays the wires inside from people wrapping the wire around the controller. Everytime....take apart, strip, cut, solder, heat wrap, hollow out flex joint to give it more bend, reassemble. I was doing this so often I once bought a lot of 6 'broken' xbox controller for $20. All were frayed, took them apart, cleaned,washed, soldered. Sold them as refurbished for $15 a piece.
Consoles all have mechanical and electrical components they all go through wear/tear and heat cycles. So I just assume at some point some parts will need service.