If this optional parameter is set, it will enable Time Banking, which can be used to limit the longest possible user session for the user to a pre-paid limit. If TimeBanking is enabled and if the “subaccounts.timeleft” column for the user is not NULL, then Radiator will use it to generate a Session-Timeout reply attribute. This has the effect of limiting the user session to the number of minutes specified in the subaccounts.timeleft column.