I generally think through purchases very carefully, but I have had some impulse buys. As stated, they have sometimes worked out to be some of my best acquisitions.
It is funny - Phase One was covering all the "needs". Self defense, plinking, whatever.
After I had the needs covered, it was Phase Two - the "wants". I would set out to get something I felt I wanted and would not be satisfied until I got it.
After wants were largely satisfied, that's when I started doing Phase Three - impulse buys. Needs and wants are covered, and now I'm in a better position financially to do modest impulse buys. This was unthinkable during Phase One, where it would take months to scrape together enough resources to make a purchase. As a lot of people are saying, as long as you don't get a real dog you can generally get your $ back, if you are the selling type.
As storage and older age become more and more of an issue, I anticipate Phase Four - the wind-down. Or "thinning the herd" or however you want to put it. But I'm not quite there yet!