Re your first question, there are numerous interesting threads here under "burn in" or "break in," such as this one:
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1173351750&read&keyw&zzbreak+in
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1173351750&read&keyw&zzbreak+in