If we configure the OpenAM 9.5.4 to use persistent cookies using following configuration inside
"Configuration" -> "Server&Sites" -> <server> -> "Advanced":
And the OpenAM is also configured with domain cookies, the Persistent cookie is only generated if the Debug level is set to Message. Note that this same configuration works on OpenAM 9.5.2 for any Debug level.
Checking the class LoginViewBean.java at setCookie() method, we can see that this problem seem to be a side effect of the fix "
OPENAM-667 Persistent Cookie should only be set on success and not on AMAuthCookie" which only gets the time to live value if the Debug level is set to Message.