Is 'needing' someone a component of being in love, or is that just co-dependency?

When I was younger, or when relationships are new or when love is in its ‘thinnest slice’—“barely even friends” it seems it has traits of co-dependency. That is, your sense of well-being is based on how someone responds to you. You can be elated and inspired and hopeful and literally floating (well, NOT literally but you get the point) or, if rejected or unrequitted, in the depths of despair, discouragement, depression. It can hurt to the point that you feel you need medication.

Good and bad, the emotional roller coaster is not always fun and can be stressful in the extreme, but good or bad, makes you really feel alive and the whole world glow—or be gloomy or melancholy in uncertain or despairing times. Even mature persons go through this in new relationships, I have observed.

But later in a relationship, you may be committed to your partner, devoted, and responsible for their needs—but it seems that the ‘feeling’ disappears once you stop ‘needing’ the person.

(as a side-note, this may be why “clingy” and needy people are never attractive)

So, is ‘needing’ a person, at least a mild dose of co-dependency, a necessary part of in being in love?

Also: How do you preserve or revive the feeling?
How do you know its time to let go, if ever?
Can a person be in love without needing that person or building their life or emotional well being on?