As per usual, Ubisoft is setting terrible precedents for the gaming industry.
According to warning emails they've begun sending out, they'll be starting to close inactive Ubisoft accounts after a thirty-day grace period, permanently revoking access to potentially hundreds of dollars' worth of games and DLC. While the exact length of time that constitutes 'inactive' isn't quite clear, any other launcher you care to name (including Steam) will let you log on and play your games even after not touching them for years, no questions asked. It almost seems like a phishing scam on the surface, but Ubisoft's own support has confirmed that this will be the policy going forward:
If you needed any more proof that physical ownership is the way to go, this is it. A desperate move to drive up player retention? A way to save money on server costs? Good old-fashioned French spite? Whatever the reasoning, it's another characteristically underhanded policy.