Really kinda up to you to decide how much and how far you want to do. We all develop our own styles. I do not monitor my ppm levels when in soil. But, I use a different nute line and system. I've done DWC, flood and drain, coco,etc and when hydroponic, I do monitor pH and ppm. Personal experience, soil grows don't require the monitoring that soilless takes. Obviously there are exceptions. And, usually all that monitoring pays a weighty dividend at the end.