I'd do them one a day - I find that Hubtraffic . . . decreases if I do too many too quickly.
But the honest fact of the matter is that you shouldn't care as much about Hubpages traffic as you do GOOGLE traffic.
The only thing to consider is that if . . . .people don't look at your hubs because you publish too many too quickly - that they won't hit those Facebook "like" things and won't take the time to "tweet" them.