Oops, almost forgot. When to turn it on (you don't want them all blinking their lives away in the cooler): sense when the bottle temp is less than the ambient temp by a predetermined amount. This will work even in Blighty where, as you know, we like our beer a tad warmer* than in The Colonies.
(*"Why do we drink our beer warm?" you ask? Easy: Lucas makes refrigerators, too.)
Psst: Mr. White? I don't mean to rain on your parade, but printed films + LED *dice* ain't exactly news - not even when applied to beer-bottle labels.
Look mate, forget LED dice and bonding wires and all that. Rather, print the whole bloody thing as a pattern of OLEDs, along with a printed battery to run the show.
Next, think about making the label able to sense when the bottle is near empty (by sensing the bottle temperature, for example) so that it can alert the barkeep on the patron's behalf. How? Strobe those pretty OLEDs in a predetermined pattern that says, "Another round, please."
Now *that* would just ooze awesomeness, don't you think?