Ever notice how most tours start with a back-to-back date, followed by an every other night deal...sometimes there are other 'back-to-back' dates, but the idea is to get your voice nice and calloused over so you can sustain the pressures of singing/screaming for 2 + hours every or every other night.
The voice gets stronger and stronger, but when you stop using it, it goes to hell....as Stephen Tyler said, 'Use it or lose it...'
Axl Rose is probably just warmin' up....you will notice that when his voice starts naturally getting more grittier and it's not just the 'technique' (because that style of singing is just a technique)...his range won't be as 'high' and then everyone will bitch about that. If his voice is 'high' and helium esque, it's because he is taking care of it; it's actually stronger not 'weaker.'
Give him a few shows and it'll be just the way you like it, but the range may suffer as the vocal folds swell.