Routine is important, particularly when you are warming up. Routine gives you a benchmark by which you can judge your progress. For example, if you play the same flam progression warmups everyday with a metronome, over time you will notice that you can play those progressions faster with good quality.
However, it is also extremely important to improvise or freeform during your practice. For example, yesterday I wanted to work on dexterity and sound quality moving around the toms. I didn’t have any preplanned patterns that I was going to work on, I just sat down and whatever came out of my hands was what it was. Very liberating, and it injects some freshness to your practice routines that will benefit you down the road.
