https://forums.factorio.com/viewtopic.php?p=528025#p528025

As an addendum - using critical path method, once you've identified a particular atomic critical path to it's lowest possible amount, that is likely your optimal run time.

eg: For wave defense with its small copper patches, copper becomes a critical path - even with speed modules in the miners. Even if you max out miners at the beginning, lowest possible theoretical time is likely around 20 to 30 minutes as RCU/LDS requires a lot of copper.

See here for more discussion:

https://hbr.org/1963/09/the-abcs-of-the-critical-path-method https://www.speedrun.com/factorio/thread/xg6w1