[daper]

One of nice options in recent versions of OpenSSH is the "expiry-time" key option you can put in authorized_keys. There are also other options handy to restrict the usage of the key, for example you can limit the key to be used only as a jump host. One can combine them so the users on the jump host will not be able to execute any command and even not able to edit authorizd_keys file and remove the "expiry-time" option.