I think songs allow you to put the pieces together. Hammer on, chords, double stops, etc... so you will still be practicing many of those concepts you have been learning.

I grapple with the balance and also the time I have to play guitar. I am currently trying to work thru a song so I find myself spending more time therefore the progress of the lessons slow down. I'm fine with the trade off but know that I need to continue forward even though it is slow going.

So I say find the balance that keeps you interested enough to keep picking up the guitar. If that balance changes (as it does for me), adjust accordingly. My goal is to simply enjoy the journey and get a little bit better.