The American Academy of Matrimonial Lawyers (AAML) recently published a new guide, called the Child Centered Residential Guidelines, which outline various model custody arrangements for children of all ages. You can find a copy of it on the Resources Tab of my website.
I've had a chance to read through the Guidelines and I've got to say, the AAML did a great job! Clients frequently ask me what's a "normal" custody schedule, and I tell them that there really is no normal as every family is different, but I can provide them with resources and guides to help them determine what's best for their family.
A custody schedule that works for a 10 year old isn't likely going to work for a 3 year old, plain and simple. Typically, the experts recommend younger children seeing each parent on a more frequent basis, as otherwise children tend to forget the other parent. So, when a child is younger, a week on, week off schedule probably isn't a good idea. Once children are older, a week on, week off schedule might be a better fit though.
If you need help coming up with a custody schedule, take a look at these guidelines!