Instead of a lengthy time to answer, why not narrow it down to a specific time slot that is fair to members in different timezones? A 6-hour time slot in the middle of the afternoon (3pm - 9pm, for instance) would work fairly well. If you want a longer time, 12pm - 12am would also be appropriate for the majority of the membership.

Otherwise, as long as you start each round at a reasonable time (read: not 1am) it shouldn't matter if a person cannot answer. As long as their isn't a penalty for a member not answering, I see no problem moving on down the line.

Second topic: Because Levian said so.