DS will be 5 months tomorrow but he will generally have his longest sleep 2 hours after wake up in the morning - between 60 and 90 mins - then maybe two or three 45 min naps. We had a sort of 4 month regression where he lost the ability to nap but maintained a good sleep through at night - about 10 hours. So you know, win some/lose some :)
His naps also vary depending on what time he wakes up, which has a knock on effect of how many naps he gets in the day. But in general, I try to get him to sleep every couple of hours. I read somewhere that even a ten minute nap is fine, which made me feel a lot better about the settling/sleeping ratio.