...but if the estimate comes out to be 2 hours, and its 200% off and it really is 6 hours, I would at least know I didn't set something wrong and it is estimating 16 hours.

My guess is it would always estimate lower than what it would be.

I chatted with SM Tech support a little while about it.

At least in P9, rendering is done in memory, I could find no temp files being made or changed, there is logging you can tun on in the INI, but they dont think it logs render info, the progress bar is basically dividing your scene by buckets (i.e. bucket of 32 = 32x32px, so a scene of 800x600 = 469 buckets) and moving after each bucket is completed.  Nothing is going out to debugview.

So...only option I can see would be "Spying" on the progress bar, and tallying a running average per bucket of the progress bar...using that to estimate "time to completion", which would get more accurate as the render goes on, in most cases.