You'll never have a problem with your wife if you have the same "Deal" I have with mine.
When I first got into DSLR photography, I knew it might be expensive, and I was beginning to encounter resistance from Mrs Rupert when I bought my first expensive lens. The usual complaints....same ones you hear.......too much money, "you're obsessed", that's ridiculous, etc.
So I made this deal. Every time I buy a lens or body, I will give you an equal amount of cash for whatever you want to do with it. Haven't heard a word of complaint since.....but I do hear "when are you going to get some new photo equipment?" I have mentioned the D700 a few times and explained to her why I won't switch systems.......but she has encouraged me to have two systems. ( No, I won't)
Now it is expensive, and it makes you think hard before you buy......my last purchase in May was a Sigma 10-20 HSM 3.5 and a Sigma 17-70 HSM OS 2.8-4.0....ended up at around $2200.......but I bought them for vacation, and during the entire trip all I heard was how nice she thought it was that I had two new lenses for the trip! Imagine what I might have heard without the "Deal"!
I love my Pentax gear, and have no other Hobbies. I love Mrs Rupert too, but do have a couple of "Daytime Girlfriends"......
Life is good...and fun, enjoy it!