Apparently there’s no rule regarding how long a business pitch should be, it depends on the presenter, content, product etc. Yet one should know that it shouldn’t be very long that it gets boring and tedious or too small that it does not even convey proper meaning.
Ideally 18 minutes is considered perfect time length as discussed in one of the TED Talks, but again its no rule and could vary. Though TED organizers have discovered that 18-minutes is the ideal length of time to have a serious discussion without putting an audience to sleep.