I dunno, talk to:

1. Other singers, find out how they look after their voices
2. A voice coach of some sort.
3. A doctor. A lot of medical problems can hurt your voice, e.g. LPRD (when stomach acid comes up into your larynx--I have this)

I once heard an archived interview with Pavarotti on how he cares for his voice. He said he treats it like a "lady" and said, for instance, that he avoids eating spicy food.

Here's another example. Training regimens for marathons generally don't involve running a full 26.2 miles before the marathon. Maybe there's a way you could save your voice for performances?

Water, water, water....