Tummy Time Strike

Ruby's pretty good with tummy time. She'll go a good 5-10 minutes before she starts to fuss. But lately she's learned something very important: she doesn't have to work at all...all she needs to do is lay her little head down and take it easy. Now, when I put her on her tummy, she'll keep her head up for a few minutes and then just call it quits, and that usually involves sucking her thumb.