I think the real question is more the timing of each part of the event. Whether it’s a wedding or a corporate party, the formal events should take about 2, to 2 1/2 hours. For a wedding, I’m talking about dinner, toasts, bouquet toss, father daughter dances, etc. For corporate parties, we’re again talking about dinner, awards, gift giving and any special events. The further away from this the event goes the quicker guests will leave once these are done. I once did a corporate party that had four hours of formal events. Once the dancing started, three quarters of the guests left (more like bolted) before the first dance song was even halfway done. Now each event is different, but this seems to be a good general rule.
On the other end of things, I think it’s a good idea to leave guests wanting a little more. Do you want to go that extra hour, when there is a core group of people still dancing, but the party has slowed down. Sometimes if you go further, the party can just fade away, instead of keeping that sense of excitement. I know, I just reduced my own pay, but it’s a valid question.
Again, each event is different and needs to be evaluated on it’s own merits, but these are issues to keep in mind when planning.