We run many (hundreds) of instances in most/all AZs, and this appeared to be about 30 minutes of flakiness in EBS instances created during 2012 (roughly) in onl

We run many (hundreds) of instances in most/all AZs, and this appeared to be about 30 minutes of flakiness in EBS instances created during 2012 (roughly) in only one us-east-1 AZ (Amazon randomizes the names, so my us-east-1e is different than yours). Data point in favor of Amazon.