I think your regex will omit the last number in the string. Although I've not graduated to actually using lookaheads, I believe that's what (?!.*\d+(\.\d+)?) is.
This works:
Jim
You're entirely bonkers. But I'll tell you a secret. All the best people are. ~ Alice
For he does not know what will happen; So who can tell him when it will occur? Eccl. 8:7