--xyz-duration not working, not even in sandbox

[Gaspa79]

In Firefox it appears that when one sets the duration variable, nothing happens.
In Chrome I get inconsistent behaviour overall.

Just wanted to report this, thanks.

[mattaningram]

I just tested it out in Firefox in the homepage sandbox and the --xyz-duration variable appears to be working for me. Can you show an example of it not working? Also what is the behavior you are seeing in Chrome?