sbiddle: My dealings with both VoIP and PSTN ports puts the figure at around 60 minutes on average between the number moving from the losing service provider to the gaining service provider. I obviously can't comment on the timeframes other providers may have. Mobile ports are also very efficient and take around an hour.
I was impressed with 2Deg porting from VF. I don't understand why it takes so long for 2Talk. But I don't think we lost service very long and I could have done more to minimize down time if I'd cared.
As I only move my numbers once every 3 years, does a couple of hours of down time really matter?