My DS (7 months) has just started to have longer naps (he used to only sleep for 45 mins so was having 3-4 sleeps per day) but now naps up to 3 hours so tends to have two sleeps - one about 9-930ish, another after lunch, and then bed about 6-630ish, but its not set in concrete, I just go by the tired signs. Someone told me babies tend to get more active around this time (6-7 months) and therefore tend to start to sleep longer - not sure if this is the case or just a random coincidence I think every baby is different - some use more energy and will be more tired, others are chilled out and 'relax' more so need sleep - so try to go by your baby's cues if you can, this will suit them best