When a getMore is executed, we reset the cursor's "idle time" value to 0 prior to plan execution. We then increment this value via ClientCursorMonitor thread during plan execution. This means that a cursor returned by getMore will have 10 minutes minus getMore execution time left before timing out. A getMore command/op that runs for 5 minutes will be left with 5 minutes until timeout on return to the client. A getMore that runs for 10 minutes will be eligible for immediate timeout. We should instead start the timeout period at the time the ClientCursor is unpinned.

A fix for this issue should take SERVER-28327 into account, as it will likely change the mechanism we use to timeout cursors on mongod.