Good catch. To better answer that, I probably should explain a little how its all working. There are 2 actions you can do with SCRYPTmail:
- Send Email
- Receive Email
When you send an email, you encrypting with public key of the recipient. (In reality its little different, you encrypt email with symmetrical encryption like AES, and AES key get encrypted with PGP public key ) That generally apply to any PGP emails providers.
When you receive email you using private key to decrypt email and can read it in plain text.
It's pretty simple to this point. What differs SCRYPTmail from other providers, is that most of them store received emails in such PGP format permanently, which essentially will get old and be susceptible for an attack. Like 512 bit PGP keys become insecure.
With SCRYPTmail in other hand, when you receive email, AES key gets copied into user folder object and discarded from email. Doing such way, your email are stored always encrypted with AES-256, and PGP part of it discarded at the very moment you receive new email. To keep this way, you just need to login regularly into your mailbox to check for new emails.
So answering the question: no. With SCRYPTmail you don't have to re-encrypt email every 3-5 years, or until AES-256 show major flaw. What you need is regularly login into account, or if you decide not to use it anymore delete account from settings panel.
However with other encrypted email services, which using same PGP encryption, they should be concerned their emails get compromised in a few years.