I run a logistic robot based system with individual buildings receiving and sending items with chests.

With logic I can connect the input or output inserter to the roboport and only feed items to the chests if the total number of items in the robot network is under a certain amount.

The other big use is cycling power between solar and steam. Plug in the steam power's water pump to an accumulator and set it to turn off when the accumulator capacity is over, say, 50%. This way you won't feed excess power to the network and waste fuel.

At what stage do you find "wasting fuel" on power an issue? Early game one x red-belt of coal will supply fuel for electricity generation. One you go to solar + accumulators you very quickly don't need steam power anymore unless you're going robot heavy, in which case you'll just stamp a small nuclear plant.

...because I want to spend 5 hours optimising stuff like that? =)

My base is a total clusterfuck and not a perfect city grid of maximised train-based transports to hyper-optimised factory blueprints. Just the way I like it.

The first effective use you stumble across is oil refining chains. Only turn on heavy cracking if heavy oil is backing up, etc.

Found my project for tonight, "thanks" I guess? :D