Recall training assistance

I have never successfully trained a dog with any kind of decent recall so we’ve always been stuck on leash even when we have access to acres and acres of land. I now have a 4 month old gsd who we’ve been working on training constantly since 8 weeks old, just started heel today and knows “between” where he sits between my legs. After I was out training him in the yard today we were just walking around and the leash got wrapped around my leg and I forgot to grab it, he was probably 20ft away from me at that point. When I called him to heel he actually did (with some extra bunny hops mixed in). I call that a success with my previous track record. My question is, how do I keep this going? He knew I had treats in my pocket, I’m sure he was just performing for food but I want him to always come back to me.