Is there a max duration limit?
Currently, there is an artificial (technical) five-hour limitation per conference. You can hold as many conferences and as long as you'd like, but at the five-hour mark your call will be ended. You can simply call back in if you need to remain in the conference.
What happens if my conference goes past the scheduled duration?
Nothing! Seriously, your conference can run as long as the limit of five hours. The reason UberConference asks for a specific duration is that this duration will be saved and passed-on if you or your participants decide to export the event to a calendar (Outlook, Google Calendar, iCal etc).
Can I enter a custom duration?
Yes, you can enter any number of minutes for the conference duration. Simply click into the field and start typing.