Whether you want to consider a prenup or not, it is always a good idea to know what the rules are. As a general rule it is true that separate property remains separate property even post marriage. However, in practical terms it is not that simple. What if you add value to that separate property post-marriage? For example, if you own a classic motorcycle before marriage but you restore it post-marriage. In the absent of a prenuptial agreement, the community will have an interest in that " separate property."
Some people think prenuptial agreements are inconsistent with marriage. How can you in one breath say "I want to spend the rest of my life with you," and in the next breath say "but if it fails...." But that is the wrong way to look at it. Better way to look at it is to treat it like life insurance. You hope you will never need it but if you ever do it is there to make things easier.
Take the motorcycle example for instance. While the above hypothetical is true, did you know you can change the rules? Yes, you can; that is the whole point of a prenup: "My motorcycle will remain my separate property no matter how much community funds and efforts I invest in it."
In fact, you can opt out of the entire community property system altogether. (The only thing that you cannot get out of entirely is spousal support; you can, but it will be subject to an unconscionability test and the test is done at the time of dissolution.)
Therefore, even if you don't want a prenup (it is not for everyone), a short appointment to go over your assets and liabilities now could potentially save you hours, and thousands of dollars, down the line.