This is an unanswerable question. What if you decide that you should have experience with three men before choosing who you will stay with "for good." What are you going to say, "Well, you're the man of my dreams, but I need to get it on with two more guys before I settle down, so wait." What's a "real" relationship? What makes you think that you will stay with the person you think you are going to stay with for the rest of your life, for the rest of your life? What if you put everything you have into the relationship and make sacrifices and don't get what you need in return? What if your "life partner" lies to you, or changes, or falls in love with someone else and dumps you?
I have always approached my relationships honestly, with the intention of carrying the relationship as far as it will go. If I dated someone and didn't really like them, then I broke up with them as kindly as possible. But you never know, you can get twenty years in and find out it was a mistake, or that your partner isn't who you thought he was.
I think I just vented. Sorry.