Tempur-Pedic

My question is this:

Take a Tempur-Pedic mattress, for example.  I can't live without my Tempur-Pedic pillow.  Well, maybe I'll live, but I will have periodic serious shoulder/neck nerve pains if I sleep on something else for an extended period of time.  So I've always been a Tempur-Pedic fan, and after sleeping on a Tempur-Pedic mattress for a mere two nights at a hotel, I was sold.  I really hope, that when I'm older, I'll be able to afford a Tempur-Pedic mattress.

But I can live without a Tempur-Pedic mattress.  It will be a luxury.  A $1,500 luxury, double any other very good mattress.  Is this greed?  Yeah?  Can't I justify that by saying, "A good night's sleep is important for having a good day.  Investing in this will help me wake up better every morning and use that day better to do work that glorifies God."  Is that legit?  Or is that just an excuse?

At what point do we turn God into an excuse, a rationale for something only we want?

Obviously, if you're out there killing people in the name of Christ -cough-Crusades-cough-, you have crossed the line.  But what about the more subtle ones, like the mattress?