We used a dummy with Squib 'till he was about 3 months old, at which point he seemed to be more interested in playing with it than sucking on it, so I binned it. Squib was a bit of a rubbish self-soother, which meant until about 8 months ish I was either feeding him to sleep or using the pushchair. He's now able to settle himself, so like someoneorother said, what seems impossible at one age, can suddenly change when they're a bit older.
TBH, I 'm a middle class snob don't really like dummies, and have a friend whose kid ended up a late talker and with his jaw out of alignment due to having one in constantly until he was 2 and a half, which kinda put me off 'em - bit of an extreme case I know. I reckon whey they're still wee though, go with what works...