Game too fast or just me?

Yes it basically has to do with the rate of income compared to how fast you are using it. The bigger the numbers compared to the storage amount, the more storage you need because the fluctuations are more extreme. Energy's numbers are 10 times as big and so you need more storage earlier.

But because you can get so much metal so quickly you should still start building them pretty quickly. Early you can get away with just a couple or none at all, but within 10 minutes you will need to start building large batches.

We need a bigger storage unit basically.

Problem with emptying your storage at all times also is that you will build things slower and require disproportionately more power. If you have metal saved up for a rainy day then you can commit a lot of build power when you need it and get things done ASAP, instead of turning things on and off trying to divert power to the flux resistors or whatever.

It's one thing to theoretically optimize build orders and all that, it's another to have the resources that you need when you need them in practice.