Usually I make some tea. If it's not strong enough I let it brew a bit longer. If it is delicious I call it a good brew. If it has brewed for too long then I would probably say that it has been stewing too long and is too strong.
Infusion - The process of pouring water over a substance, or steeping the substance in water, in order to impregnate the liquid with its properties or virtues (OED, http://www.oed.com/view/Entry/95690?redirectedFrom=infusion#eid).
Brew - To make by mixing several ingredients (ale, beer, and the likeJohnson), as whisky punch; or by infusion, boiling, and fermentationas tea. (OED, http://www.oed.com/view/Entry/23126?rskey=gcAh2Z&result=3&isAdvanced=false#eid).
Stew - To undergo stewing; to be cooked by slow boiling in a closed vessel. Also (of an infusion of tea, etc.), to ‘stand’ on the leaves, etc. (OED, http://www.oed.com/view/Entry/190084?rskey=81G847&result=6&isAdvanced=false#eid ).