My apologies, I was thinking of issues on the hardware or api end that might have a limit.
I am using the axidraw control in Inkscape v21.0 on Windows 10.
The plot was running for several hours and then I went to bed while it was still running. when I woke, the plot was unfinished and the pen was back in the home position and inkscape + the axidraw control were still running. My monitors did goto sleep, but not the computer (tho I will admit I am still figuring out how windows makes those distinctions)
The groups only seem to go 2 levels deep. I did run the axidraw optimizer and I am wondering if something happened there.
At any rate, I was in part curious about upper limits :)
I am trying the file again while I am awake and see if the problem happens again. Thanks!