If you're in a league that has a limit on the number of starts your pitchers can have in a week, it is critical that you look at your pitching schedule for the upcoming week BEFORE you start making moves. The majority of leagues have a limit of 12 starts - to maximize this you can use 11 starts Monday-Saturday and then start as many as you want on Sunday. You only get penalized when you hit 12, but penalties don't roll over into the next week so breaking the limit on Sunday is fine. Once you count the number of starts you have scheduled until Saturday, you can determine how many streamers you'll use for the week.
If your count is off, you'll run into weekend problems. Just like me this weekend. It is important that you keep an eye on your starters' schedules, as rainouts, injuries, and desired extra days of rest can shift rotations mid-week. I had a rainout this week and an unexpected rotation shuffle - somehow I ended up using 10 starts Monday-Friday but having two scheduled starts Saturday, putting me in danger of losing my entire pitching staff for Sunday. I'm in a tight race again, so now I'm going to have a bench full of probable pitchers tomorrow.