Is passphrase required each time?

I have a certificate from a vendor, I have trusted it and certified it. When I went to encrypt a file, it asked for my passphrase. Is this something that I do just once or will it remember it from here on out? The reason I ask is this…

I am setting up a script which takes a file and runs the following command:
gpg -se -r UserId filename

then the script takes that file and ftps it off somewhere. I am wanting to set this up as a cron job and if it prompts for the passphrase, then it will hose the script. Unless, that is, I can pass that phrase into the original command.

Any insight would be appreciated. Thanks