MSG timeouts for Ethernet messages are forever in most cases, compared to your need to know. It is not always possible to change that timeout value and easier to just roll your own.
Your messages probably complete in a second or less 99 percent of the time, but I would simply time the duration after they are enabled and not done...monitor that number for a while, maybe trap the peak values for a few hours...
Then set up your own TON to monitor the condition (EN, not DN) and set the preset value safely above what you know is normal. If the timer ever gets done, latch or seal a fault bit. Ultimately, when someone unplugs a cable or some other problem occurs along the wire and other switches involved, you will "know it" in a couple of seconds and can take appropriate action in your logic.
