This command prevents a nick or room from ever expiring from lack of use. However, a room will expire even with keep on if the founder's nick expires or is dropped. If you wish to keep a room, set keep on for the room and the founder's nickname.
Example:
/msg nickserv keep Jenn|fer on
/msg chanserv keep #webchat on
This is useful for any official room on your network. It is also useful for your own nicks and the nicks of other people who help to run the network. Official nicknames should be protected because they may become recognized and trusted. These nicks should only be used by their owners to prevent others from abusing that trust.