(setq erc-log-channels-directory "~/.erc/logs/")
(setq erc-save-buffer-on-part t)
(defadvice save-buffers-kill-emacs (before save-logs (arg) activate)
  (save-some-buffers t (lambda ()
                         (when (and (eq major-mode 'erc-mode)
                                    (not (null buffer-file-name)))))))
(add-hook 'erc-insert-post-hook 'erc-save-buffer-in-logs)