"More than 3 days a week at home and you start to lose the benefits."
As someone who has been exclusively working remotely for several years, I'm not so sure about that. I guess it depends what you consider the benefits to be and from which side of the employee/employer fence you're on. Are the benefits that you have a more relaxed and free adult life - in both work and play? Or are you looking for a hack to try to forcibly increase worker productivity beyond that which is attainable with a full time in-office approach?
When working just a couple days a week or month remotely, it can feel like a nice break from the distraction-filled office life and so it's natural to treat it as such - maybe you work harder/longer to get the most out of it so as to not squander the special time and privilege. When you're home all day every day, you have to pace yourself or else you'll burn out in a matter of weeks - same as if you worked sun up to sun down in the office everyday. That self-pacing could feel/look like suddenly it becomes less useful to work remote all the time, but I think the reality is that people can only work so hard for so long no matter where they physically locate themselves. (And each person has a different threshold.) If the "work from home 3 days a week" thing is really nothing more than a piece of "aren't we an awesome place to work" cheese dangling in front of the employees noses, I think eventually that backfires and people burn out more completely (and cynically) - so they begin to slack off on those days at home and think of them as a good time to take a "much deserved" break by "sneaking" out to have fun during the day. Inevitably the company responds by requiring phone checkins during regular office hours, demanding you be online/IM/email/webcam at certain hours, snidely pointing out how long it takes you to reply to a message, etc. At which point, you might as well go into the office everyday because, frankly, you are getting none of the true benefits of working from home anyway.