My misses lets me get what I want within reason. With things like tubes/tyres/lube it's just a straight out purchase. With things that cost a lot, I tend to talk to her about it, but she always says that I will buy it anyway.
The other day I was talking to he about my current build (CDF) and it was her that said I should get a black team pro ti to match my new bike, as It's a white/black/silver build and my current one is honey. She just said that I will build one up soon that the honey will match again. I was quite taken back.