Depends on your net/practice objectives.
If "grooving" or developing muscle memory for new shots/skills, I like to take my time and think thru the session. But those sessions are pre-planned and done with either a machine or a handful of like-minded players.
If objective is general practice and development of rhythm, then practice imperfectly. No matter what level you play, match conditions are hardly ever perfect to whatever story is running thru your mind. Let there be distractions, loud people, "chirping", people rushing thru the practice, or whatever distraction you can think of. Why? It helps the mind focus on technique. In my experience, when I get tired or get "triggered" by something, first things that leave my game is my technique. Developing that skill where you can employ your technique under hard conditions is rewarding in the long run.