url-cookie-save-interval

url-cookie-save-interval is a variable defined in `url-cookie.el'.
Its value is

3600

Documentation:
The number of seconds between automatic saves of cookies.
Default is 1 hour. Note that if you change this variable outside of
the `customize' interface after `url-do-setup' has been run, you need
to run the `url-cookie-setup-save-timer' function manually.

You can customize this variable.