Sounds like you've been burned before.
I was married for 12 years. Then she became a teacher, qualified and totally changed. So I divorced her, there's a lot more to it. This was some 14 years ago. On hindsight, I wished I didn't get married, it was really against my better judgement, but it happened, because she wanted to get married.
Marriage wise, she turned out immature and selfish. The funny thing is, the guy that she's met and got married to since thinks she's the one, lol.
If you're both traditional, it'll probably work, if one or both isn't, I would personally keep clear.
I have a girlfriend, she knows I would never marry her. My mate who was best man at my wedding has been 'sternly' told to shut up about me remarrying. He's finally got the message.
Prenuptial agreements are binding in the US, but not in the UK.