It depends. It's definitely not something I'd set everywhere. It doesn't look at the time queries take, it looks at their cost and that's an estimate. It doesn't stop a running query, it prevents queries from even starting if their cost exceeds the threshold set.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability