I'm also quite curious about the estimated print time, because for my first use it is double what the slicer says.
New to OctoPrint, Raspberry Pi etc. and still a newbie at 3D printing.
Have printed a dozen things sliced with Cura3D on my Creality Ender 3D, the print time would never seem to be off, maybe a couple minutes for a multi-hour but still simple item (on finer resolution and average print speed).
Just created an updated version of an item, which takes a good 4 - 5 hours ...
5 hour print
Uploaded the gcode via OctoPrint to the Raspberry Pi 3B and let it start printing.
An hour into the print, I check in via the web interface: 9 hours remaining?
10 hour print
I'm currently also not seeing any progress indication on the progress bar on the printer. It is printing the base, the slowest part of the item, but still ...
Guess I'll know in a few hours and update.