Components (of all kinds) basically burn in once when they're new -- but let me qualify that: this is true if what one means by "burn-in" has to do mainly with "setting" or "forming" the interfaces between conductors and dielectrics (not just wiring, but capacitors, diodes and many small devices. The only time this process MIGHT (depending on certain circuit design issues) need to be repeated, would be if one moved (as Rushton mentioned) and it turned out that the AC circuits for the audio system in the new house were on the opposite phase of the electrical service from the ones in the previous house.
Another instance of component "rehab" which I do perform on a regular basis (I'm just not sure "burn-in" would be the correct term) is using one of the many "system enhancer" CD's which supposedly remove residual magnetism and molecular stresses (Oy!) which build up in components, speakers, cables, etc. This could be identified as borderline snake-oil, were it not for the fact that most of them produce noticable results; except, for your cartridge/phono preamp, you'll need a record with a frequency sweep like the Cardas test record.
Speaker cables and interconnects should not need re-burning-in unless for some reason they accidentally (or on purpose?) get removed and then re-installed in the reverse orientation. Why? Because it's a bit like reversing a non-polarized capacitor in a circuit, and the interface between it plates and its dielectric have to be "re-formed" by the new signal polarity which (from the cable's point of view only) is now 180 deg. out of phase with the previous signal.
Another instance of component "rehab" which I do perform on a regular basis (I'm just not sure "burn-in" would be the correct term) is using one of the many "system enhancer" CD's which supposedly remove residual magnetism and molecular stresses (Oy!) which build up in components, speakers, cables, etc. This could be identified as borderline snake-oil, were it not for the fact that most of them produce noticable results; except, for your cartridge/phono preamp, you'll need a record with a frequency sweep like the Cardas test record.
Speaker cables and interconnects should not need re-burning-in unless for some reason they accidentally (or on purpose?) get removed and then re-installed in the reverse orientation. Why? Because it's a bit like reversing a non-polarized capacitor in a circuit, and the interface between it plates and its dielectric have to be "re-formed" by the new signal polarity which (from the cable's point of view only) is now 180 deg. out of phase with the previous signal.