I use the Iris Tornado (freeware) with no problems even for flights of 30 minutes or more .....
But .. but ...
I use also for recording flights the freeware (very good) FSrecorder
The problem is when I replay a recording with the Tornado .. after maybe 1 minute .. the sim begin stutter .. and also the sounds change to a horrible thing
.. following by a alarm message about memory !! 
This occur only when replaying a recorded flight with the Iris Tornado
I suspect a gauge problem
Of a hundred of aircraft in my sim .. this the only one with this probs
Anyone with such same bad experience ?
But .. but ...
I use also for recording flights the freeware (very good) FSrecorder
The problem is when I replay a recording with the Tornado .. after maybe 1 minute .. the sim begin stutter .. and also the sounds change to a horrible thing
This occur only when replaying a recorded flight with the Iris Tornado
I suspect a gauge problem
Of a hundred of aircraft in my sim .. this the only one with this probs
Anyone with such same bad experience ?