Since your commenting *"For convenience, but also because I don't want to accidentally change the password and lose information"* I'd suggest using a **keyfile** instead, it won't change. And gpg wouldn't know what cached passphrase you wanted to use when symmetrically encrypting a new file anyway.

But storing and using a keyfile safely becomes an issue. Storing it encrypted should be safe.

- Using a very small LUKS container should store and decrypt it safely
- Or store it encrypted in a gpg file, and extracted to `ramfs` (note `tmpfs` could be written to cache).

Then you can close the LUKS container or delete the file whenever you want to, and not worry about entering the passphrase correctly the first time if you only relied on gpg-agent's own caching.

Or, just use a gpg public key.