Burn in question and evaluation before burn in

I am wondering if there is a general rule as to which direction any burn in would be heading

Seems to me to be pretty logical that the answer would be no. Obviously it would be dependent on the type of component (amp, cd player, preamp, speaker, interconnect cable, speaker cable, etc. etc.); and on the technology used (tube, solid state, dynamic speaker, electrostatic speaker, cone driver, dome driver, ribbon driver, electrostatic membrane, etc. etc.); the specific design of the particular example of the component type and technology, etc., etc.

I agree with Shadorne's comments as well.

Regards,
-- Al

There are too many variables involved for any reliable comparative conclusions to be drawn over such a time span.

I agree, unless the differences in the particular case are very great, AND extreme care is taken to rule out extraneous variables. A few possible extraneous variables which come to mind include the following; there are undoubtedly many others as well:

Ongoing aging or burn-in of OTHER system components; seasonally-related temperature changes in the room affecting component performance; changes (also possibly seasonally-related) in line voltage, or in noise levels on the ac line; if records are used, subtle wear in record grooves due to repeated playings; and last but certainly not least, improved perception by the listener of subtle details in the music, due to repeated listening.

Regards,
-- Al