Killing idle pooled connections On SQL Server, I'm trying to prevent connection from staying open. From here I understand that Connection Lifetime allows a connection to stay alive for a certain period of time since it was opened.

Quote: When a connection is returned to the pool, its creation time is compared with the current time...

Is there a way to do something similar, but with connections who are idle? When they return to the pool they'd be allowed to live for X seconds until killing them, unless they're used again.
The connection pool will automatically kill connections which haven't been used in a while.  There's no way to identify these from the SQL Server side with 100% accuracy without running the risk of the client application throwing error messages when it attempts to use the connection from the pool which it things should be open put is really closed.

What problem are you trying to solve for?