I'm something of a seat-of-the-pants brewer too. I quit writing down my recipes, I create them on the fly, I will get an OG measurement but no FG, just generally lazy about a lot of this stuff I guess. I play with no-sparge, no-chill, and BIAB. Beer still comes out good. Can I reproduce something if it comes out good? No but I know the next batch is going to be good so I don't need to.