My wife, generally, doesn't care what I spend on my hobbies as it is my money. We do, however, usually discuss purchases that are more than a few hundred dollars. A $3000 purchase warrants more discussion now that we are in a larger house with a new toddler and her working only part-time now.
I'll look forward to a 600mm when I'm 50! (It'll be a nice addition to my D900!)