For me, I always start the week by playing my goalies and then I re-evaluate after that. You don't want to sit them too early and risk an injury ruining your stats for the week.
There are a lot of different options available to you once you've got 2 of your 3 starts. Ward is a solid option but if he starts out rough, you can sit him down and roll with Rinne for the rest of the week as it's rare for him to get shelled.
If you get behind in GAA and Sv%, you pretty much have to start them all no matter what as you have nothing to lose.
If you have a big lead in W/SO and you're happy with possibly winning 2 out of 4, sit em down. I own Rinne and I almost never sit him.
The only time I sit them all is if my opponent is out of starts and I have the lead in 3 of 4 cats.
Hopefully this helps a bit. I'll add more if I think of anything.