I just bought one more, bringing my total to 19. The latest addition was a bit of an impulse purchase - a blue oxford cloth suit from J. Crew, and was actually the first thing that I've bought from J. Crew in over 20 years. The idea of a suit of oxford cloth just sounded to interesting to pass on. And to my great surprise, it turned out to actually fit me perfectly and was well worth the $250 or so it cost (including tax and shipping).
That actually makes the sixth suit that I have that really counts as an impulse purchase. The others include three RRL suits that I picked up on business trips to NYC, a J. Press York Street casual cotton suit that I picked up at the YS store in NYC and a fairly expensive Zegna model that I bought at the Tyson's Corner Nieman Marcus basically to kiss up to a potential client when I was doing financial consulting.
When I was in my 20s I had sort of a mental list of the various suits that I wanted to have one day. I actually have all of them now, so I may actually never buy another suit again. So unless I see something really exceptional, I don't ever see going from 19 suits to 20 suits.