Yeah, like chrpwrs says, it is pretty common for glow plugs to die during or right after break in, due to the very rich conditions.

As far as the fuel line goes, those rubber lines can withstand some pretty impressive temps, but if it does get too hot, there is a chance of the fuel vaporizing and causing "vapor lock".
But, when your unit flips over, the fuel level in the tank is now at the top of the tank and if the tank isn't right full, the level will be below the intake point in the tank. SO if you have longer lines, your unit will stay running longer than with shorter lines, simply because of the fuel capacity of the lines and filter.