I gave my son a Heinz Teething Rusk for the fir...

I gave my son a Heinz Teething Rusk for the first time today and he loves it! I'm just wondering at what point I should take it off him and chuck it out. He is 6 months old and has 2 bottom teeth so he can chew into it a little bit and bits come off it. Any help that can be provided would be appreciated as he just loves them and I am hoping he can still have them.