It's just the usual UPS cap, that at some point the computer is not able to handle everything in time?
With the tools provided, it's very easy to duplicate your factory again and again.
But it's not really a problem, which can be solved without compromise. If you had a computer, which is double as fast as now, you can play ~1h longer to double your factory
If you play multiplayer, you might have a look at clustorio, which scales with count of computers.