Miniature Australian Shepherd Question

So I have 2 mini aussie puppies and they are getting along very well. Was wondering what is a...

So I have 2 mini aussie puppies and they are getting along very well. Was wondering what is a good way to get them to sleep longer than say four hours. We take them on separate walks and the older male knows five commands at 12 weeks. The younger one knows 2 commands. But no matter how much we run them and much training time they get they won't sleep for more than say 4 hours without wanting to play more.