Love is patient, love is kind... love hopes all things, believes all things, bears all things. (That's my abridged and paraphrased version of what it says in 1 Corinthians 13)
Love is not a casual, throw away phrase with no pronoun in front of it.
When I hear "love-you-bye" as someone rings off a phone call, it makes me want to shake that person and say, think again! First of all, where is the personal investment? You didn't even put the "I" in front of "love you" -- so your personal investment is minimal. Saying, "Love you" is not anything like saying "I love you." Don't believe me? Try it sometime and see for yourself.
We throw around this phrase "love you" (or even worse, "love ya") a bit too frequently and too casually as a culture.
Love bears all things -- that means it's a commitment, an act of the will even when the feelings aren't warm and fuzzy.
Don't just toss it out there. Mean it. Invest in it. It's love, after all.