Wouldn't it depend on why they split? If it was his insecurities that drove them apart, then I agree, what makes you think this time will be any different. If it was her that ended it because she had grown uncomfortable with the situation then this girl could be completely different.

I don't think this is one of those black and white situations where you can say it didn't work before and it won't work again. I think this is a situation where you have to analyze what went wrong the first time and make your decision based on that.

That all being said though I tend to believe that some things are better left as fantasy.