Maybe a dozen pieces, including date and time, after boot-up.
It is rare that I have more than half a dozen additional others open, even after hours of use.
It is my habit to open programs to use them, and close them when I finish. I generally prefer to open and close a program a dozen times during a day than to simply leave it open. Same with internet tabs.
Perhaps I am too concerned with "lean and mean" but when I started working with computers (1984) one of my instructors bought a new computer. In a "bragging" conversation, he told one of the other instructors that he had 384K of RAM. "Three hundred and eighty-four K! That is obscene!" was the reply.