Listening to what you want when you want. Eating what you want when you want. Drinking what you want when you want. Shopping gets done very quickly. Farting in bed and not being compared to the spawn of hell. Same as the last for belching, but you only get called a pig.
I have all those. And the benefits of marriage too.
The idea is to take your time before you make the committment in the first place. Our society's overvaluation of romantic love keeps people from getting to know each other well enough to really know whether this is a person they can stand to live with for 50 years...and who can stand to live with them, as they are, for the same period.
Watch out for "Once we're married, I'll get this person to straighten out and do things my way." Either in your own thinking or the other person's, or, Gawd forbid, both.
Just my personal take base on one person's experience.