DS's wake time at night varies...normal?

Happycouple

I think that DS is a pretty good night sleeper so Im not complaining.  We put him in around 8ish and normally sleeps a 6-8 hour stretch and then a 3ish hour stretch.  For example, he more frequently sleeps from 8:30pm-3:30am and then down again from 4:30 -6:30am.  

In the past 4 nights he has slept until 2:45 one night, 3:30 1:45 and 4:30 the other nights.  Anyone elses DS do this?  I cant recall when it became more consistent with DS#1, but I think around 2ish months. 

I feel rested, but wish I could predict his wakeup time a little better.  We always have the same routine and do the same exact thing before we put him in.  I EBF except I always give him a bottle of BM right before bed so I make sure he is getting a certain amount of milk.