I like the wisdom on "when and how" to share the good news of another car purchase with your wife.
It takes a few years to develop, but I have seen "strategic confusion" used as an effective model. You need to have a modest amount of space available, and it is enhanced if you also have some offsite storage for cars. Periodically have a buddy put his car in your primary storage where your wife will see it. When she asks about it, say, "that's not mine, its Larry's". If you keep this up for a bit, she'll lose interest, forget exactly what you own, and stop asking.