If you haven’t heard about the Institute for Vocal Advancement, then check out their website here http://www.vocaladvancement.com/
This organization is run by a group of fine teachers, mostly of whom are previous master teachers from the Speech Level Singing organization run by Seth Riggs.
I believe this organization has much to offer both students and teachers. It is the same sound instruction that SLS offers by a group dedicated to staying in touch with the latest developments in vocal science.
I have quoted a section about technique from their website below. It is well said, and explains to singers exactly why we need to exercise our voice regularly and correctly.
Why is Technique So Important: Singers don’t have frets like guitar players, or keys like piano players. We don’t have a volume knob. In order for us singers to change pitch and volume we have to rely on finding and maintaining vocal balance. Problems start when that balance goes out of whack. Unbalanced vocal qualities like singing too airy, too husky, too tight, too squeezed, or too pushed, can contribute to throwing your voice out of balance.