He likes to think that he'll always be there for her because he respects her and had grown to enjoy her odd wit and determination.
Which is bullshit.
If he was going to be brutally honest with himself (and this situation calls for brutal honesty) he can't imagine going back to the way life was before he met her. That sometime over the past three years she'd worked her way into his system and now was refusing to leave. He wonders what it would be like to have sex with her, he knows it would be better than good (and once he'd had a taste he wasn't sure he'd be able to not have another).
It's not an addiction, you can't get addicted to someone (that only happens in movies and books). You really can live without someone, and if she died it's not really the end of the world (nor is it the end of the world when she's with another man).
But there's a soft little voice in his head always whispering to him. Rile her up just once more, this is the time you'll really listen to her and not get turned on by her flashing eyes. Get her confused for the last time (she far to adorable when she's confused). God forgive him but he listens to the voice because it's right it will be the last time he annoys her to see the fire in her eyes and it's the last time he'll make an obscure pop culture reference he know she won't get just to see the confusion written so clearly on her delicate face.
It's not an addiction, the voice whispers, it's only an addiction if you're losing, and he's not losing anything by being around Bones.