This command lets you set how many days without use it takes before a registered nickname will be dropped.
/as services set nickexpire 25
As with CHANEXPIRE, the larger the expiry time the harder it will be for new users to find available nicks. But the lower the expiry time the more difficult it is to keep them. The nickexpire should probably allow for moderate vacations or temporary loss of internet access without causing the user to lose a nick, but still be small enough to clean out unused nicks. Especially since some people will register nicks and either forget they had them or become bored with chat and stop altogether. A limit between 20 and 35 is probably good.