Just in case a shorter version appeals to you, I think you could rewrite it like this:

  timeout 60 bash -c 'until is_ready; do sleep 10; done'

You'll need to `export -f is_ready` if it's a shell function. That's assuming you can use a timeout instead of number-of-retries.

http://man7.org/linux/man-pages/man1/timeout.1.html