I guess I'm a bad example, or my monogamous wiring is showing. For me, "I love you" *does* say that I prefer you above others, and also that I want to spend my life with you. I *rarely* say I love you to non-romantic partners--my children, OF COURSE, but (don't judge) my parents raised me to not say I loved them. My MIL tries to force it from me, and I hate it. But that's a tangent.
My partners are all what I would consider long-term partners. When I say, "I love you" I mean you are special to me, I commit to you, I will take care of you when you need it, and you are my family. When I say it, it's special, because I don't say it to a lot of people. However, weirdly, when someone is special to me, but not in the "I love you" category, I tell them to be safe. The only one who's ever figured that out is Easy, who gets me.