Most of the time it is accurate for single parts.. I print small parts in batches.. With acceleration turned on and lots of fast travel movements, the estimate can be off by as much as 40%. Easy test... print a bunch of 1/4" pillars with a 3/16" hole.
I think the easiest way to fix this issue is give the user control over a print speed time and fast travel time modifier in the process file.
There is room in the Advanced Tab Or Other Tab
Build Time Estimate Behavior
Default Print Speed Time Modifier %
X/Y Movement Speed Time Modifier %
Then in the print time gui, post the software estimated time along with the users modified time.
and while you are at it.. Supply a modifier for the Auto Arrange Spacing.
I love the software...btw...