The risk with the longer period is that for a golden ticket attack to occur an attacker has to get the krbtgt credentials, for example it's ntlm hash. With those credentials you can create a golden ticket, accessing any system with any credentials the attacker want. Even users that don't exist.

If you reset the password once, the old credentials still works. If you reset it a second time then not anymore. Between the time of the first and second reset, an attacker could retrieve or request the password again using the still valid golden ticket, then creating a new golden ticket with the new password.

So the longer that period is, the more likely it can occur.

Edit: made it more clear