From viewing, I would say it takes 30-40 seconds to test any given dialling address. I think it is reasonable to assume that in any given day, although the gate MAY be used 24-7 for incoming teams, outgoing ones will only go out during "daytime working hours". Either way, between say 8am and 6pm the gate is probably only in use for 10 minutes each hour (pure supposition).
Therefore, 60-75 addresses an hour can be attempted, which is perhaps 500-750 per day, that had previously been found "dead".