I'm going to spend a lot on my girlfriend for christmas
Why do you want to spend a lot?
She will feel appreciated and she will love me.
That sounds awful sweet of you!  You're going out of your way to make someone you care about feel special.  I'm sure she'll appreciate it!
I don't care. It's not like I have anything better to do.
I would think you do care, which is why you are doing it. She will be happy and you will feel appreciated, it's a win-win.