Respect your servants’ availability to commit.
Not everyone wants to serve on the worship team every week. Not everyone wants to serve twice a month. Not everyone wants to serve once a month. Whatever your team’s preferred level of commitment, honor it.
ONE EXCEPTION. Don’t place yourself in a situation where only one person EVER plays guitar, keys, etc. You’re crippling your team. Even if it is three weeks on/one week off, make sure you have SOMEONE else (maybe 2 or more someone elses) they are alternating with. Otherwise, you are going to be up a creek with a paddle when your ONLY drummer goes out of town or has an unexpected emergency. The band is always better when the “other” guy has played with it regularly.