First, let me start by saying my wife is a saint for putting up with me in general and this crazy audio pasttime in particular. I can only imagine what she thinks when I propose spending significant amounts of money on things that she just doesn't hear and are not that important to her. Fortunately, she believes that if it's important to me it is good enough for her.
That being said, she has voiced several opinions (I won't call them "objections" because she didn't say absolutely "no", but I'm smart enough not to push it).
1. No room treatments in the living room. My system started out as our home theater set up in the main living room. Because we don't have enough room for a dedicated listening room "those cloth things" are banned from the corners and on the walls of the main living room.
2. No loud listening past 8 pm. We have some disagreement over the definition of "loud", but lets just say that I rarely can listen at my preferred listening levels except on the weekends because we have small children that are asleep by 8 pm.
3. The boxes. I have all the original packing material for most of my audio purchases and I think she dislikes that clutter more than the actual system in her living room. The large speaker crates in particular take up half of one bay in our garage.
4. No buying 3 or more of the same item. This is not really a stated objection, but whenever I get 3 or more amps, 3 sets of speaker cables, 3 pairs of loudspeakers, etc. I can see by her look that one needs to go. I guess 2 is OK for comparison, but 3 or more of any particular items tends to be seen as overkill. This must be why I want to start a second system.

Within the above parameters, I can get pretty much anything I want as long as we can afford it and it doesn't require going into debt (credit card) or take the place of a "family" expense, such as monthly bills or saving for the kids' college, etc.