We suddenly encounterd problems with a backup software connecting to the hosts.

Finally we reallized the password aging is enabled by default and it expires after 90 days.

This is of course only a problem if you have a service or application which tries to connect through a fix user and password.

Here the commandline how you can change/diable the passdword aging for a useraccount:

passwd -x -1  -w 7 -n 0 username

You can also turn if off for the ESX server completely.

esxcfg-auth --passmaxdays=0