The ImapIdleChannelAdapter runs a PingTask every 10 seconds; this sends a NOOP to the server.
However, it has no effect on the IDLE session because this "Ping" occurs on another socket - a completely different IMAP connection.
I discovered this while writing a test server for mail support in the Java DSL.
It turns out that the second call to openFolder causes a second session to be created for the NOOPs.
However, the Ping NOOPs (which cancel the IDLE) should be increased above 10 seconds and made configurable in 4.1.