I've done it numerous times in baseball/football in 12-team leagues. We usually alot 12-24 hours per pick, which admittedly seems long. However, it's never been a problem; everyone usually picks in a very timely manner and the long limit is mostly protection in case of life emergencies. I think in my 10+ years of doing email draft we've only had a handful of people go over the limit, in which case we skip them until they notify the commissioner they're back and ready to make a pick. Then, after the person currently on the clock picks, the original person is reinserted into the queue.
Anyway, it normally only takes a month or so to do the draft. If you have motivated owners, it can go quicker, but you always want to leave time. It really just depends on how much of the preseason/spring training you're willing to forego. That's the single downside, though the benefit is that you can end up with some nice late round pickups.
Lemme know if you have any questions, though, more than willing to share my experiences.