the VTAM ID changes even for a constant terminal, so it's pretty useless.
well... the situation is not that simple
usually for generic/open terminals is ok to have everything dynamic ( IP,NETNAME,TERMIDNT)
and have everything based on the logon USERID
there are situations where it is advisable to go the other way ...
static IP, static NETNAME assigned ( tcp parms )to a fixed IP
permissions based on the NETNAME
( user allowed to logon to an application only from a specific terminal , HR is typical )
so situations might vary according to different security and privacy concerns