I think a potential way to do this is to offer lifetime plans that do not get new features, etc. that other plans often do, unless the user wants to 'top up' their lifetime plan. Effectively, they pay a large sum for a lifetime of whatever it is they want, which they can add to (so if they start with only ProtonMail but then want ProtonVPN, they can add that lifetime for another amount after the fact - but also if they already have all of the current Proton services but Proton increases the storage space for ProtonDrive subscriptions for other users, then lifetime users can pay an additional fee to be upgraded to that amount of storage as well.

Either that, or something like 5-Year Plans would be fine too, I guess.

I disagree with this. This would lose value to the customers when Proton wants to upgrade and integrate new features.

This is a stupid idea just like the people suggesting 5 year long subscriptions. Proton doesn't operate for free, they buy their own servers, maintain them, add new updates etc. and this all costs money. If you have a lifetime plan then that allows Proton no flexibility, if people pay let's say $500 and the cost of operating their servers doubles, they start losing money while with yearly plans they could at least balance out that lost revenue but not with lifetime or 5 year long plans.

Don't agree. In my opinion, timed plans keep the company having to innovate to keep the customers, and I like that.

Proton CEO already said that this doesn't aling with their mission in https://proton.me/blog/sustaining-mission-over-time.

"Proton services are never going to be the cheapest, we’re not going to have flashy promotions, unlimited “lifetime” plans (unless it’s for charity), or offers that are too good to be true. Not just because it doesn’t suit us, but because it doesn’t suit the mission."

Life long plans make sense for something like a download, but Proton makes more sense as a subscription service since there are recurring maintenance costs for Proton. I would rather subscribe to Proton rather than have Proton go under or sell out due to an eventually unsustainable business model.

A suggestion similar to this already exists: https://protonmail.uservoice.com/forums/935538-accounts-payments/suggestions/15938065-lifetime-plan , you can vote on it :v