I always get suspicious when I hear about people's "10+ hour a day" practice regimes. There are certain limits that every human being adheres to (even the master Vai himself), and when one surpassess these physical limitations one suffers the ramifications (carpal tunnel syndrome, tendenitus, etc.).

I'm not a doctor and I don't claim to know how each and every person's physiology works, nor I am I calling Steve a liar, but I do tend to get suspicious when I hear about these super-human practice schedules.