"juanon" writes:

Even if you don't pre-heat the vessel by pouring boiling water in it, its
temperature may vary a great deal. A thick, cold mug is going to pull the
temperature down a lot further than a warm bone china teapot!

Of course you are correct as you state this. But a thick, cold mug will hold
heat longer than a thin bone cup or pot. It's a matter of rate of heat
transfer. In the long run, the tea will reach ambient temperature; it will
get there more quickly with a thin vessel. There is no possibility of it
becoming colder than that (unless the vessel was pre-chilled, and I assume
that is not the case).

This time of year our kitchen is chilly in the morning, and when I make my
Irish Breakfast (same blend for probably ten years now) and pull a cold cup
out of the cabinet, I'm needing to heat extra water for that pre-heating of
both pot and cup.