I think we're getting our metric units confused here.
The teapot I use for 1-2 people for very good aged sheng is about 50-60 ml
(2 oz.), not
60 cl (20 oz). For an everyday quality loose aged sheng, I use pots between 90 ml - 110 ml (3-4 oz).
I like using very small pots for a few reasons: 1) I like my tea very strong, and I try to push teas to their limits. In other words I generally try to make teas as flavorful, potent, and complex as possible, without crossing the line into overly bitter or overbrewed. This means using a very high leaf to water ratio. 2) I try to drink only high quality tea when possible, and I can't afford to fill up larger pots, unless I have guests. 3) To me a pot of tea is like a good book- it should take you on a whole journey with a beginning, middle, and end. If I use a larger pot and less tea, then my "book" may only have about 5 chapters or plot twists. If I use a smaller pot and a large amount of leaf, then I have many more infusions (each one unique), and my book then can have 10-20+ chapters and plot twists. For me, drinking 5g of a 20+ year old well-aged puerh cake in a 180+ ml pot would be the same as reading the Cliff Notes of A Tale of Two Cities
, rather than the novel itself. But that's just my opinion.