If the NHL smashes 4 games per week into a schedule, I think you'll see a lot of coaches pre-setting their goalies as a 3:1 split. Three per week for the #1, one for the back-up.
This would be only 75% starts or 36/48.
I think a workhorse like Kipper or Rinne would start 40... but I wouldn't count on any higher than that for a smashed schedule.

On the front-end of the schedule, I think a goalie could be seriously worn down if he plays too much too soon.
So - that's another case with back-ups eating significant games.

It will be the last 3-4 weeks of the schedule - where you'll see a lot of teams leaning on their #1 only, because of confidence and importance of every game.
Niemi (SJ) was a good example in past years... the Sharks went heavy on him only later in the schedule, giving him every start in March.