DD is 7 months and in the last month had finally started napping for more than 40 minutes at a time (wahey!). However, her night-time sleep became terrible at the same time and she would often be awake at night for hours for no obvious reason.
This last few nights she's slept better at night - still waking 3-4 times but just having a feed then going right back to sleep. But she's back to 40 minute naps in the day!
Her routine is very roughly
6am awake
8.30am nap
11.30am nap
2pm nap
6-6.30pm bedtime (wakes once between this and 10pm, then at 10pm (feed) then again around 1-2am and 4-5am)
So at best around 13 hours, which surely isn't much for a 7 month old baby 
Or have I just got one who doesn't need the sleep?