When singers or bands go on tour, how do they prevent hoarseness?

I mean, when you take a look at a band's tour schedule, it's like every couple days they perform for months at a time. How do they do their throats recover so quickly? Also, what happens when a singer has a cold and has to perform? It's to do with their vocal exercises. They also drink lots of warm water and oil believe it or not it sooths the vocals.