When you expand, you sacrifice the "strength of your army" (i.e. tech + army units) for a while. What is this duration? To illustrate what I mean, here's a makeshift graph of 1-base production versus a 1-base into expansion production:
My question is: How long is that green line? How can you measure it / calculate it?
The paragraph-style description of the graph is: While you save for the expo, your army is not getting stronger. When you build the expo, you can continue to produce on 1-base, but you will be behind the cost of the expo. Once the expo is up, your income will gradually increase, allowing production to accelerate. At some point the acceleration will elevate you past the point you would have been if you stayed on one base.
I have a very hard time sensing this moment in the game. It's easy to feel when income increases, but hard to know when the expo actually led to a stronger army relative to if you hadn't expanded.
There are a lot of factors that influence the answer of course, but they can be ignored as follows:
- What race are you? For example if you're terran, you can benefit just by building an orbital command and summoning MULEs. Or just double-producing SCVs. Assume building right at the expo location as this is more general. If you're protoss, assume that you build a pylon at the expo, but that you needed it anyway so it's not really a cost of expanding.
- Will you need gas geysers? Ignore gas, because the geysers cost minerals but return gas, and cannot be compared. It would be a separate graph entirely.
- How many workers can you transfer, how saturated was the base where they're coming from, how far is the transfer? Assume transferring a practical handful of 5-8 workers. If you are transferring more, then there's not much question: you apparently NEED to expand regardless of the return, because you're over-saturated.
- How many resources are remaining in your other bases? similar to the last item, if you are desperate to expand, then it's not really necessary to calculate when it will be advantageous
- Unit producing structures you must create in order to . This could actually be considered as part of the cost to expand, however it can also be ignored because the goal here is only to find point 4 (on the graph). Beyond that is not so important, because you know you're benefitting.
So the idea is to get a general sense of "+/-30 seconds, how long is this duration?"
I think this would be helpful making in-game decisions, calculating riskiness of expanding (balancing need versus risk of being attacked during the green line), for developing new builds and considering FE, or making in-game adaptations. Or just plain curiosity.