primary key expiration and subkeys

Hello all,

Is it normal behavior to add a subkey whose expiration is after a
primary key only to have the subkey be flagged as expired after the
primary key expires? If so, it may be good to issue a warning during
--edit-key that a subkey expiration is later than the primary since one
would have to change the expiration of both the primary and subkeys to
make use of them.

Thanks,

-- 
Ben Kibbey