I'm trying to find out some information about SQL Server 2012 Enterprise Edition with AlwaysOn replication; either synchronous or asynchronous.

The replication is fine, but, can you find any information about what's classed as "too high a latency" for synchronous replication? Microsoft just say "you can't do it over long distances" which means nothing.

Ideally, I'd like to find latency recommendations for synchronous and asynchronous. And also, if asynchronous, how big a time frame of data could you lose if the primary server goes down.

Any sources would be good!