One of the best ways to set yourself up for a distraction-free Sunday service is to have rehearsals that allow for more freedom on Sundays. God deserves all glory for services that usher people into His presence, but he's all also called us to lead his church so there are steps we can take to steward that responsibility well as musicians. Part 1 was adjusting your language from "practice" to "rehearsal." Part 2 was about the importance of preparation. The next part is all about punctuality.
Ultimately one of your main objectives is to attain and retain trust from your musicians, so you've got to focus on being a good steward of their talents and their time. When it comes to time, I want to make sure that I make the most of their time, and one of the best mindsets I've adopted is to try to never steal time from your people. They are being generous with their time, and for many if not most churches, they are doing for no compensation. You do not want to exploit their generosity by stealing time from them through your own laziness and sloppy leadership. Being punctual sends a clear message to your people that you value their time.
REHEARSAL START TIME: You need to guard your start times. I've found that setting the expectations of punctuality works great when it's based on two times; a "call time" and a "hard start time." The call time is when you are suggesting most people to arrive to set up instruments, visit with each other, ask questions about songs...it's just a time to get settled in prior to the start of rehearsal. The hard start time is the actual beginning of rehearsal. I've found that call time should be at least 15 minutes prior to hard start, but no more than 30 minutes prior to hard start. Some musicians won't need to arrive as early as others, but setting the expectation of people to arrive at whatever time they need to arrive in order to hard start at a certain time is what works for the people I've led. You need to feel the freedom to hold folks accountable to their punctuality, and of course, before you start holding folks accountable on that, make sure that you are leading the way in your own punctuality.
REHEARSAL END TIME: Punctuality is often associated solely as being on time at the beginning, but we also need to make sure we are being punctual with ending rehearsal in a timely manner. As the leader, you are solely responsible for how long rehearsal lasts. You can be punctual with when you start rehearsal, but if you allow for rehearsals to drag on too long, then you've lost all credibility and focus from your people. I've found that some best practices for ending rehearsal on time are to begin the rehearsal with the most familiar song (and if possible the most energetic song), then follow that with the least familiar song, then progress the rehearsal so that you end with a familiar song. This does wonders for the psyche of your band members by starting and ending with songs they are confident in playing, it kick starts the rehearsal in a nice way so that everyone's engine is running efficiently when you get to more difficult/less familiar songs, and then you can end rehearsal on a high note. It just keeps rehearsals flowing. Another best practice is to not allow a specific song or part in a song to ruin your punctuality. If a song, a part, or a musician isn't meeting the standards you had hoped for and it's negatively impacting your ability to be punctual, then just leave it where it is. You can make adjustments and do fine tuning during the week prior to Sunday, but don't steal time from your musicians but trying to achieve perfection at rehearsal if it's just not happening.