How can I safely use Get-Credential to obtain a username and password for a set period of time for use as command line arguments?

Credentials in the form of SSH keys can be stored in memory using SSH Agent; However, if clicking the wrong link, or running a malicious program they can also be snatched from memory and sent somewhere else; which is why ssh-add offers the -t option to specify how long keys will be kept in memory before one is required to reload them hopefully using a passphrase.

Powershell has simalar functionality using secure strings but we are discouraged from using it, especially when writing credentials to disk; but Powershell offers another option in which you can prompt a user for their username and password, store it in a variable that will last the length of the powershell session: https://stackoverflow.com/questions/47069785/use-encrypted-password-for-plink-putty

Is it possible to unload credentials gathered from Get-Credentials from memory after a set period of time, similar to ssh-add?