In reply to Jeff Chandler.

Ok then, they offer "unlimited" support, and you can use their themes on an "unlimited" number of sites. This is taken from - http://www.studiopress.com/faqs

"HOW MANY SITES CAN I USE THE THEMES ON?

You can use any theme package you purchase as many times as you’d like, on as many websites as you desire. The purchase of theme packages allows you unlimited use of the themes, as well as unlimited support.

In other words, we do not restrict your use to a specific number of sites, or a specific period of time in which they can be used. "

Jeff, you stated that "WordPress product businesses that operate with unlimited anything are almost certain to fail as it’s an unsustainable model"

Do you think StudioPress are almost certain to fail? How much time do you think it will take them to switch from an unsustainable business model?

I think subscription models are the most viable method for most WordPress businesses, but you can't ignore the elephant in the room - one of the biggest theme vendors does use an "unlimited", non-subscription based model.