One way of measuring progress is if a something that was once difficult is now easy. I used to have a hard time constructing walking bass lines, let alone improvising them. Now I worked out these lines several separate chord changes and can improvise variations on them, such as Autumn Leaves (in several keys), Blues (in several keys), Rhythm Changes. It is still difficult for me to play these lines while I improvise over them on the right hand.
I am good at knowing what I like in these lines, and can avoid what I don't like. The basic rules are to outline the chords and have good voice leading, which usually means that beat four will lead easily to the root of beat one of the next chord. The other rule is that they shouldn't be too corny sounding or obvious, but still very convincing. Then I could get into having them be phrased confidently, being in the pocket and being truly jazz like. So this is still difficult in some sense: not just having the notes, but having it sound really good and then also doing the improv over them. Just knowing what you want is a huge step. How could you possibly achieve anything if you didn't know what you wanted?