headshot,
breaking in as in running the pads with mild/sensible driving speeds and try to avoid hard braking situations. this is to ensure that the pad surface will mould so to speak, according to your rotor surface. because your rotor's surface isn't really flat, it could be warped a little. that's why u've gota break in the pads...oh also i think it's to let the pad and the pad plate to bond correctly by supplying adequate ammounts of heat to melt the 'glue' that they use to bond both materials together.
swv,
sorry, i'm a small time dealer only haha. anyway, the way pads are tested here in malaysia are basically by word of mouth with no specific factors being taken into account. most of them test it like by driving really fast and brake before a corner when the pads are new, crash(or not) and then complain that the pads suck. therefore, i would say that the only people who actually have more experience in testing pads properly wouldbe MME teams and R3. but even then, it all depends on how the person drives. some MME teams that use the mintex1144 would need to change their pads 2-3 times during the race whereas some can last the whole race! (finishing position not taken into account here).