For me, five is plenty and I'll probably stay with 2-4 once the old ones pass on.
I think that the one-on-one relationship between dog and human is vitally important, and that each dog deserves an hour (minimum) of quality time per day with their person. Younger dogs need even more time as they need additional exercise time. So for a normal person working eight hours a day, sleeping eight hours a day, with an hour transit time, two hours of "self" time (on the computer, showering, cooking, watching TV, etc.) that only leaves five hours for dogs. And that means no more than five dogs (especially given that two hours of "self" time is really not very much).
Do my dogs each get a full hour every day? Not exactly - the younger dogs tend to need more time, the older dogs tend to sleep more and 10 minutes of petting/massage a few times a day is enough one-on-one for them usually. They all get group time where we play games with toys (whoever brings the toy gets the treat!) or group sits/downs, etc. in addition to the one-on-one time.
But if I had unlimited resources, I'd love to build up a rescue/"out to pasture" kind of facility for abandoned, unwanted, unloved dogs. While I don't think that living without the human interaction I posted about above is a good option for a person's own dogs, those poor unwanted dogs would be better off in a facility that catered to their needs as much as possible than to live in tiny concrete runs or wandering around starving on the streets. I have this vision of a facility with lots of employees, huge areas with indoor/outdoor sections, indoors with music or TV or radio, dogs grouped together in successful social packs, etc. It would sure beat being tied up outside on a cold night, wouldn't it?
Anyhow, just a dream .. in the meantime, five dogs is my limit .. *L*
Melanie and the gang in Alaska