Watching the stars burn down won't be as much fun without him.
ETA: We're American, so Amerocentric advice is likely to be useful to us.
I'm sorry this is a nice sounding and romantic, but useless answer. It was Valentines day yesterday, I was bombarded with enough relationship related cached thoughts as it is.
Or are you saying the other person will literally die or refuse to ever interact with you if you don't "marry" them? Also do you expect US government granted 21st century marriages to remain enforced then? Indeed do you have any evidence whatsoever that a stable relationship can last that long or is likley to without significant self-modification? In addition why this crazy...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.