Subscription plugins?

Everyone who pays for software seems to have an opinion on subscription models, not often positive. I can understand, though, how for some people it actually works pretty well. Let it go on the record that I would never (as in never ever) move my Illustrator plugins to a subscription-only basis, but timed licensing is supported by the online authentication software I have (kudos to NSP-Code for a great product), and it got me thinking that it may be a nice option to offer. Sometimes a job arrives with CAD files that could make a nice starting point for the project. Rather than manually trace it all, it might be nice to “rent” Concatenate for the duration of the project and reuse many or most of those vectors. I think a lot of people would agree that the twenty bucks for Concatenate is pretty small compared to the savings it returns in its first project alone. Or when you divide a ten-dollar plugin into a few months’ fee, it pretty much comes down to pocket change. Then again, maybe there’s a situation that works for both parties, like one year’s access to Productivity Pack or a site or corporate license. I’m open to suggestions!