Probably good advice for any piece of hardware, but I did leave this scrolling patch running today with a paragraph's worth of text for about 4 hours without any issues. I even cranked the metro up to 1ms for a while, and although it was difficult to read the LED
still no issues. But these are CC messages. Sys-ex is a totally different story as the protocol was never intended to accommodate "real time" responsibilities.
In fact, I would venture to say that the sys-ex issue is probably the number one reason to use the KMI software. It is true that you can really screw up your hardware w/ sys-ex messages. Particularly with something like Max, which is always ***at your own risk***. If you are reading this and you're not comfortable with what system exclusive messages are and how they are different from MIDI performance data then I would HIGHLY recommend sticking to the ss objects in Max. (or even just the regular editor)
It's not difficult to envision a scenario where one might accidentally connect a sys-ex message to a metro that's been set to something like 10ms or less, or try to compile sys-ex inside a patch rather than bang out a fixed message and some numbers get crossed because of bad message ordering. Everything might be fine... or you could very well end up with a piece of incommunicable hardware. Unlike Jeff, I've actually seen that happen (or rather the aftermath) and it's a big bummer.
But these are extreme cases. If you're consciences about your patching and just use the two or three initialization sys-ex messages (tether, standalone, backlight) you'll be fine. I haven't and wouldn't do any more than that.