I'm struggling to find a good way of timing how long to let my cafetiere stand before drinking.
Is there a rule of thumb for how long I should leave it per mug? Or is there more to it than that?
Start with a coarse ground of coffee with about 1 ounce (28 grams) of coffee for about every 15 ounces (450 ml) of water. The water temperature should be below boiling, about 200-205° F (93-96° C).
Stir in about 1/3 of your water to let the coffee grounds "bloom" for about 30 seconds; then add the remaining water, cover it, and let it steep. The total brew time should be about four minutes. Then press the plunger to the bottom and pour.
Once the plunger is pressed, be sure to dispense the coffee into another container once that brewing cycle is done. If you let the brewed coffee sit with the spent grounds, it will start to develop a more-bitter taste and be somewhat over-extracted (unless that is an effect you are looking for).
Note: There is also a "cold-brewing" method which requires several hour of extraction, but that is likely to be outside the scope of what you are asking.
My cafetiere has the instruction that you should not use boiling water (I think the recommended temp is 85 degrees centigrade) so as to not scald the coffee and then let it steep for 5 minutes before plunging.
Personally I swirl it around a bit about a minute before the 5 minutes has elapsed just to agitate it a bit.
Grumpy Mule recommends waiting 30 secs first before pouring the water on and waiting 4 minutes they also recommend wetting the grounds first, waiting for the bloom to settle before filling with water.
For French Press, my default brew time is four minutes before plunging (i.e. pushing down the filter). I also recommend you pour it into mugs or a separate serving container immediately, so that the grounds don't continue extract at the bottom.
Every bean/roast is different, so adjust accordingly. If you find four minutes produces coffee that's a little sour or thin, add 30 seconds; if it's bitter, subtract 30. I've found that dark roasts generally need less time, and light roasts need more.