Is there any legal guide lines for how often Bingo Balls must be changed?

[vikkyner]

We have several charity bingos that are using bingo balls from 5 to 10 years ago. Several are miss matched and the paint is falking. I can not get them to buy new balls for the machine. They say they don't have to. But we get the same numbers repaeting every game - and some hardly ever show up unless it is a coverall! I need legal verification that they have to replace the balls.