My LO still wakes at 12 and 4am for a 15 min feed. That being said, she only takes 4oz bottles still and this falls within her every 4hrs feeding schedule. She can go longer and has, such as from 8pm to 2am, but then she'll wake up at 4am still to re-nurse. Yea it's not ideal for my sleep, but she's healthy, chunky and growing, so I don't complain. I expect her to go longer once she takes more breast milk at a time and after this next growth spurt.
Don't always assume it's a "problem". Every baby is different and if they're flourishing, then it's what they need at this time still.
Update: At my 6 month checkup, my Pedi said to stretch her out to 6hrs if able, especially since she's gone that long. Well, now she eats at 2am, but wakes around 1030pm and 5am, but I soothe her back to sleep pretty fast without the boob.