Before I set a min and max on buy in, we played a few nights that started out happy, and people kept reloading to the big stack. It went on like this until I had a few guys start asking me what happened to our friendly game, since it was getting too expensive for them.
I actually built a POS terminal to handle the cash for my room. That terminal tracks buy ins and cash activity, and can give me all that information. I saw that the later a game went on, the bigger the reload got. It got to the point where someone actually bought in for $500 (to match the big stack) on a .25/.50 table and that had occurred on multiple occasions. Not only do I consider that outrageous, but it also showed that the amount of money changing hands in my games was far larger than I really felt comfortable with (I just want fun games, serious games are at the casino). Mix that with players wondering how it got so expensive to play and I had to do something to bring my game back in line with where I wanted it. I set buy ins at 40 BB min and 200 BB max. The games instantly got a lot cheaper and a lot more friendly, and my players are quite happy with it.