5 hour print stopped halfway through

Tonight I attempted my longest print yet, 5 hours. Halfway through, the printer began stopping and starting, stopping for longer intervals, and eventually stopped entirely. Repetier also got slow to respond.

Has anyone else had this happen?

I shut down every other app that was running, to no avail. Task Manager shows Repetier using 364 megs of memory, the largest in the list, but that's not a lot. I have 6 gigs. It shows memory usage at around 40%, and CPU usage at around 3% -- though it spikes up to 30% then back down occasionally.

I have Slic3r set to use 3 threads, which increases memory use, but I don't know if that's just during slicing or also when printing.

Maybe this is a good reason to get an LCD controller, or at least do a reboot before a long print. It's been awhile since my last reboot.

Bummer. I'm going to leave it overnight and hope it magically starts up again, but I don't have high hopes.

Long prints are always best done from an SD card, not from an attached PC.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Slic3r only needs the threads while slicing. After that it isn't used anymore, because the actual gcode is already fully generated. For long prints I would strongly recommend
an LCD module with SD slot. There are a ton of problems a computer can have while being on for 5 hours. Even a little freeze cause of a new program starting could just end
a print. A module doesn't cost that much.

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Prusa i3 Rework (from Replikeo.com) & original Prusa i3 MK2 (from shop.prusa3d.com) << the MK2 definitely is worth the higher cost!
Print Troubleshooting Guide // Visual troubleshooting guide

USB problems are quite common from what I could read over the years.
I too struggled at times getting long prints to finnish without stopping.
The best thing I have done to ensure my prints work out is to get a high quality USB cable that is just long enough to connect to the printer.
Also make double sure all power connections and pin connections are 100%!
A problem with gound on the power supply of the printer causes the USB connection to go nuts.
One thing I also noted when using cheap amplyfied desktop speaks was that all stepper motors cause feedback on the USB line.
This was noted due to the noise coming out of my speakers even when the motors were on stop.
Disabling all motors and the sound was fine.
I could even hear the different print moves through the speakes
Adding a ferrite sleeve on each stepper motor cable fixed that for good.

Repetier is pretty graphics-intensive. I've noticed that longer prints tend to make my other programs skip and crash, because Repetier is trying to render all of the lines of the print. Try reducing its graphical settings.

I am half way through an estimated 18 hour print now with no issues.
But I am using the basic Pronterface.
Even with the 3D preview the CPU and memory usage is moderate at best, considering the G-Code is a bit over 27mb.
However I noticed some hick ups during the print where the printer stopped for about a second and the computer was totally unresponsive.
So far I narrowed it down to hardware changing, like plugging in a USB stick and programs with a high demend in HDD activity and memory usage.
To me it looks like the G-Code is transfered in relatively small packets.
And if such a transfer happens while the computer is too busy otherwise the print gets into trouble.
I might get a cheap laptop for the printing that runs nothing than a basic Windows and the print software to avoid these hassles.
Next board will get a SD card.