expiring gpg keys

[David Newman]

Michael Lucas' gpg/pgp book recommends setting a relatively short
expiration time, such as a year, for personal keys.

Would an expired key still work into the future? If, for example, I
sign/encrypt a file today using a key that expires next year, would I be
able to decrypt the file three years from now?

I've been using a key that never expires to sign/encrypt mail and files
on the assumption that keys with discrete lifetimes don't work after
their expiration dates.

thanks

dn