About one week. It's obviously a decision if you want to use them or not, but age wise I wouldn't say there's such a thing as too young.
That said, its recommended with breastfeeding not to give dummies or bottles before 6 weeks to avoid nipple confusion. We flouted both these rules (out of desperation we gave dummy before 2 weeks and expressed milk in bottle before 3 weeks I think) and Isobel never had any problem with latch. But maybe we were lucky.
As far as dummies go:
*I haven't tried taking it away yet, but we went from letting her have it anytime to only when tired without any issue
*They do help reduce SIDS risk but only slightly and imo not enough reason to use them
*They do help soothe a tired baby and can give you a break from a baby who is comfort sucking on your breast constantly (though cluster feeding can be mistaken for this), but it won't soothe a hungry/wet one of course, and you will still need to soothe your baby in other ways too, eg rocking. I know that's obvious but it p**s me off when some people say dummies are for parents who can't be bothered to properly soothe their child.
*Babies don't always like every brand, especially cheap ones. We use MAM and I've heard others on here say MAM worked for them.
