I have friends that all have different arrangments, one set have one sibling each living with them, it didn't start of this way but has ended up this way over time.
Another friend has his children thur, frid, sat, sun, mon,
then his ex has them tues, wed, thur, fri, sat, sun, mon, tus, wed,
then back to him thurs, frid, sat, sun, mon,
So he has his children 10 nights a month as he says he wants to be as much involved in his childrens lives and its like extended weekedns every other. It also means he does the mundane things like school run, doctors, dentist and doesn't just do the "nice" daddy weekends with them.
You have to work out what is right for your children and your cicumstances - everyone is different.
Get a good routine going and make sure the children and you are happy.