Courts increasingly ignore pre-nups and most people are stupid so don't even understand how pre-nups work. Pre-nups protect the assets you have BEFORE the marriage, just like a trust is suppose to protect your assets BEFORE a lawsuit or bad event. Thinking you can use a pre-nup to protect assets you acquire during course of marriage is equivalent to thinking you can put assets into a trust to avoid paying out money after you already been sued. One would need a post nup to accomplish what you are thinking. Even where a
rich man tries to use a pre-nup and was rich before he got married, courts frequently try to break them claiming they violate case law and are not equitable.
In most Western nations there is some version of common law marriage. Just because you don't propose to a woman, doesn't mean the courts will accept you are not married. If you are living 2-3 years with a woman the court will view you as married as someone who had a wedding or went to the court house.
What's the point of
asset protection to avoid 30-40% Western taxes when you are risking losing 50-90%+ of your income/wealth to divorce, divorce lawyers, alimony, and excessive child support?
The better option is to not live with a woman or if you must do so, do it in a place where common law is not recognized like Saudi or something.