When to introduce your kids to your new partner

So this is probably controversial but I was wondering when everyone introduced their children to their new partner? My ex is already introducing his new gf of a week to his kids (he has a 4 year old daughter from a previous relationship and our 4 month old son) and I feel like that's a recipe for disaster. Me and my bf have known each other for 5 months but only been dating for 3 weeks and he still hasn't met my kids (I have 3 and he has 2) and vice versa because we want to wait and make sure our relationship lasts before bringing our children into the mix. We have an amazing relationship even before we started dating but we know that honeymoon faze is always great so we want to wait at least 6 months. Is that fair? I guess I just want others perspectives on it. I think waiting is best so that if the relationship doesn't last the children won't be confused or upset when they no longer see that person they've grown attached too..