I'm as sick and tired of DRM threads as anyone, but I think this one has been pretty well behaved and ideologue-free. It's just a discussion of the business and economic model, as SteamWake said. Not a discussion of it's moral or ethical merits. So my personal opinion is I'm ok with it.
I'm not very clear as to how it would work if the same servers were authenticating multiple games. That might be what screws up my prediction - if the marginal server load for authenticating SH5 is a pittance because you're already running it on the authentication server for the latest and greatest Assassin's Creed game, then I guess you could theoretically keep it going for as long as you like without eating into the profits of the SH product line.