Ds started 'sleeping through' at around 7 months, he is bf but dh started doing a rollover/dreamfeed with formula at that time so i could get some rest. he does 7 till 7 with the feed at 10pm(although hes dropping the 10pm now) it has worked quite well for us, i like to have a routine, and ds seems to like it too - not super strict, i can be flexible but feeds and sleeps at similar times each day. he likes to know what comes next iykwim? he sleeps in a grobag, in his cot, in his room and has done since 4 months. Saying all that if he is teething or something else is going on he can be more wakeful.
these bubs are so hard to know! it can drive a person crazy wondering why they do the things they do!