This is from someone who has had to deal with a lot of vocal issues because of a physiological condition I have on my cords...so i've dealt with/talked to a LOT of ENT's:
Basic rule of thumb: if it hurts, you shouldn't be doing it...cause it's your body telling you to stop. That's why it hurts when we cut ourselves...so we don't cut ourselves more...and that's why singing incorrectly hurts...cause it's unhealthy.
With that said, it is hard (in some shows/styles, impossible) to do 8 shows a week and not have some minor vocal strain...however, the trick is to know your body well enough to know how it heals. Pay attention to your voice and it will teach you.
In addition, vocal nodes are SERIOUS business. Vocal rest is the best thing you can do...FULL VOCAL REST (especially not whispering...which puts as much vocal strain on your chords as yelling)...and follow the advice of an ENT who deals with singers...many ENT's don't get the whole singing thing...whiich is why it is good to seek out those that do.
Finally, learn a technique that keeps you in good condition, and don't feel badly about turning down gigs that you know you can't handle vocally...those of us who are young often think we can sing forever without a problem...but it just ain't true...know your limits, know your voice, and know when to shut up.
"Fundamentalism means never having to say 'I'm wrong.'"
-- unknown