[Unglued]

i noticed that the part where the 2 colours meet seperates very easily, and once there's a rip it only gets worse.

however this dosn't take out any chunks of the balls, the foam stays intact.

by limit i guess you mean when a ball would be taken out of the game?
i think as long as the ball keeps it's original shape it'll be kept in play.. since balls can be scored on either net i doubt some colour wear would get them replaced.

unless they are worn down creamy coloured balls of foam?

anyways i apart from them being ugly i don't think you should worry.