Why do cryptologists recommend changing the encryption key from time to time? Is it the same reason security experts recommend changing a password from time to time? How can one determine how frequently to change keys or passwords?

What will be an ideal response?

A
key
may
be
guessed
or
learned,
which
renders
all
ciphertext
from
that
point
forward
vulnerable.
This
is
similar
to
why
experts
recommend
changing
passwords
periodically.
The
period
of
key
or
password
change
should
match
the
sensitivity
of
the
data
being
encrypted:
more
sensitive
data
entails
more
frequent
key
changes.