I always found this exercise a bit pointless because once I factored in weather and human daily idiosyncracies (which mostly came from lack of practice) I never knew the exact average distance I hit each club. I knew that I had a very consistent swing though which meant that if I hit PW 110m one day I could pretty much count on the fact that I would need 8I for 140M for the rest of the day and so on. For me, getting a consistent swing is more worthwhile than spending more time on a swing monitor.
Moreover, if you're lucky and have some free time on course (and it's quite) just drop a few balls from the 150m or 200m mark and progressively hit some balls towards the green and watch the spacing. If you can hit it relatively straight this is just as informative as spending time on a monitor (as long as the wind isn't blowing too much).