How Long Should a Story Be?

As a reader, I like to feel the story goes on long enough for the characters to live in my head, after the story has finished.

How long is an acceptable novel-length? Genres like science fiction or science fantasy have their conventions of big,spine creasing books with many pages.
'Short ' stories vary enormously from 1,000 words upwards. Since I often write YA novels, I use 30,000 words as my guide, and yet picture books may have as few as 400 words (like the cake -eating hippo stories) despite having layers of sub text.
Short crime or mystery stories depends upon a twist at the end, and so a sequel may not be an option.

But with non-fiction memoirs, I prefer the writer to be brief and candid, rather than 'fill in' to make a word limit.
Maybe a story should be long enough for you to recommend the book to a friend or to seek others by the same writer?