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Manufacturers should break-in components. So when bought, it is ready to use. I don't believe in "break-in" periods with the exception of tubes.

Apart from a small difference in electromechanical devices like loudspeakers, there is no break-in. At all. None.

This is nonsense. Just ask any electical engineer.

I guess it would matter if it were speakers as compared to amplifiers. Same as tube to solid-state, break-in could take between a week to several weeks, 4-8 hours day

Burn in is not as important as stable operating temperatures. If it's got tubes or moving parts, a good rule is to warm it all up for 30 minutes before making any judgment calls. Speakers too. As coils warm they become slightly less magnetic, and as amps warm up they become slightly more efficient. Warm it up.

Whatever time period the manufacturer says is effective—done in the way that the manufacturer says is effective.

Depends on the component, no surprise there. My Audio Definition Duets reached peak performance after six months. Some interconnects and speaker cables seem to need weeks. NB: keep contacts clean, source components on all the time and demagnetise the system regularly.

Speakers need both extended break-in and regular use to keep up their best. Electronics' need for break-in varies a lot. Digital may need some days, analog low-level may also need a day or two to perform their best. Cables, though, just need to have their connections "setled" to do their best. Any new connection will sound different from an older one, otherwise cable burn-in is, IMHO, just fantasy, or getting used to the sound psychologics.

Approximately 100 hours or so on most loudspeakers. Components about the same. I'd recommend getting cables burned-in on Nordost's Vidar Machine.