when you go and see a band how long are you ideally looking for them to play for?
i'd go for:
new band(only 1 album or a few singles under the belt)- 30mins tops
established band (few albums, tours under the belt) - 45-60mins
long-standing/favourite band - (multiple albums, posters on your wall) - 90mins at absolute most
i can't imagine wanting to stand and watch *any* band for longer than this
p.s. gigs in theatres with seating means this all changes as i happily enjoyed the 2hours ryan adams played a few weeks back whilst sat on my fat arse