I first started this topic almost 6 years ago. Nearly 23,000 page views later, it's still going strong. Thanks to everyone for contributing and keeping this thread alive, especially Rich (egvrich).
After reading this topic all these years, and based upon my own experience and observations, it seems that having four 20 game winners on a team is more common than having a 30 game winner.
With that being said, I discovered that there is something even more uncommon than having a 30 game winner: having 4 lefty 20 game winners on the same team. I can only recall seeing it a couple of times.
I was recently reminded of this in a thread started by nomadbrad in late May entitled "I finally did it" where Brad noted that he had his first team with four 20 game winners. Here's the link to Brad's team:
https://365.strat-o-matic.com/team/1552744But within that same topic, hollywood posted his team with four 20 game winners and it was all lefty pitchers:
https://365.strat-o-matic.com/team/1556583So congrats, hollywood, on accomplishing such a rare feat.