It's not a major red flag but I look twice at any person (male and female) that take this as a major milestone or attach tremendous importance to it. I'm from the school of thought that any reasonable person would know what the real attachment was long before these words had to be said (if ever...)
But what do I know? Some people are built that way and I am not.
Reverse the question: "when are the words "I love you" enough???
I get the sense that the "I love you" line is often a monstrous trap in that one or the other party front loads a great deal of additional meaning into it. And with all those unstated, unreasoned and fluid meanings are expectations that cannot be met except by The One (who is a cartoon movie character currently playing at your local theater, otherwise he doesn't really exist..)
IMO, it can never be enough because nothing, really, can be enough for all the unexamined expectations people have when hearing this phrase becomes important.
Ok, but if you're looking for something of a poll result, I would say that we can start with cold, hard divorce court reality: most everyone who's been thru a divorce went through the "I love you" stuff, so we can count as a starting point the statistical divorce rate (50%--?, more??) for a starting point.
Then work up from there. My personal opinion is that 100% is the real answer.
