I believe that it varies with different snakes. Many imports will never become accustomed to handling. My Borneo blood isn't the friendliest, and although he tolerates handling, I highly doubt he enjoys it.
My ball python, on the other hand, has been with me for almost two years and she does seem to enjoy handling. Or, at least, she enjoys to stretch out and crawl around. Having been with her for almost two years, I have learned to "read" her pretty well. After a half hour or so out of the cage, she whips me and makes a beeline for dark places, which is her way of telling me that she's done.
But, as I said before, it varies.