I really like the Pass Plus lifetime plan, because I can rely on all my aliases being active forever.
I am interested in the Mail Plus subscription, because of extra addresses and unlimited folders/tags, but it makes me uncomfortable knowing my important extra addresses would stop working if my subscription gets canceled.
It is understandable that lifetime plans are not profitable in the long term, but the perks of Mail Plus and Pass Plus are not as expensive as providing VPN or cloud storage and Proton already added a Pass lifetime option.
Another user shared the idea to buy lifetime additional aliases and this post has been marked as planned in 2015. I want to express my need of a lifetime plan providing all Mail Plus features.