3D prints sometimes fail after several hours despite starting out line. Common causes include bed adhesion problems, temperature drift, filament issues, slicer settings that change mid-print, and power or firmware glitches. A good diagnostic checklist is to check bed, verify stable temperatures, inspect filament condition, examine mechanical parts, review slicer settings, and rule out power/firmware issues. Asking the community for their experiences and early-warning tips can be help prevent long prints from failing.
Maintenance. The longer a printer runs, the more likely it will fail.
Things heat up. Things stretch. Things sieze. Depending on how much you use your printer, regularly checking belt tension and greasing screw rods and gears goes a long way in atticipating problems.
Most common is heat creep, or tangled / broken filament.
Could be that the gods have a cruel sense of humour, Apollo is the worst .
Heat creep is worth ruling out first since it tends to show up after the machine has been running a while rather than on the first layer. Belt tension and leadscrew lubrication are fair points too; small changes accumulate over long jobs. One thing I would add is checking whether the failure happens at the same height or time each run, because a repeatable point suggests something mechanical rather than random. If it is inconsistent, the filament path and extruder grip are the next places I would look before blaming the printer itself.
The point about whether the failure is repeatable is what I’d focus on. Tracking the height or elapsed time of each failure gives you a pattern to work with, and that separates something mechanical from something random. Heat creep fits the ‘after hours’ description well, so I’d rule it out early too. On the filament side, I’d also check the spool for tight winding or drag that only shows up once the roll has unwound a fair bit.