If I were Dorian Gray, I wouldn't be giving too many shits about the aging portrait. First of all, the portrait is not even real: is just a fucking picture and it's not even a human being. I would spend my time committing sins every single day for the rest of my life, because hey, I'm immortal, remember? I have the wealth, the eternal youth, the splendor of the victorian-era mansion that everyone fancies, and I also own the most trusted servant. And don't forget the fact that my picturesquely handsome appearance and my immaculate sensibility towards art that I myself possess. On the most basic level, I'm an immutable chick magnet.
Would I still kill Basil Hallward?
Fuck no. He's a consummate artist and he painted my own portrait, which is a masterpiece (according to him), and I'd even let him be my best friend. I'd kill Lord Henry instead. Yes, that fucking influence-giving piece of shit with his flawlessly designed epigram. I'd play even around with his wife after I killed him and then kill her afterward.
The problem with Lord Henry Wotton is that he thinks he's a wise-ass piece of Socrates. God, I can't stand his statements about vulgarity and circumstances that are supposed to be good or bad.