I think the longest for me so far was about 10 hours for a final print. I usually do a quickie (low infill etc) that is around 33% of the final build time. I use a MakerBot Rep 2 and the software is pretty accurate at giving a guesstimate of the total printing time as a function of the preview. So you can play with settings to see how long something is going to take before committing the time or materials to doing a print. The vast majority of my prints are less than 2 hours. Russ