At this stage in their development, children are starting to become more independent and are more comfortable exploring the world away from their parents. They will also be able to understand the separation better and how it affects them.
They may also be more concerned about fairness and feel that they have a responsibility to be with both of you. Make sure that you reassure them that you are both fine with the arrangements that you have made, whatever they are.
Parenting patterns can involve longer periods with and away from each parent without it affecting a child's sense of security. Regular consecutive nights in both homes will be fine. As children grow, longer periods with fewer changes will often work best.
Make sure that your arrangements take account of your children's growing engagement with the outside world. They will have friends to spend time with and clubs to attend and these are important parts of their development.