function next() {
		var u;
		if ( count === len ) {
			debug( 'Finished all queries.' );
			out.meta.success = scount;
			out.meta.failure = fcount;
			return clbk( null, out, ratelimit );
		}
		if ( idx < len ) {
			u = users[ idx ];
			debug( 'Querying for username: `%s` (%d).', u, idx );
			opts.pathname = '/users/' + u;
			request( opts, callbackFactory( u, idx ) );
			idx += 1;
		}
	}
Requests user details data for the next username in the queue. Once requests for all desired usernames have completed, invokes the provided callback.

@private
@returns {void}