The thing is, I am using XenForo with Amember membership software, and the login works through amember. There is no "remember me" checkbox there and I already set that the user should be logged in forever in amember. Basically, they don't "log in" in xenforo, they just push a button called Log In which would redirect themt o amember login screen, but because amember is set to login forever, the forum just refreshes and they are logged in (without seeing the login screen of amember). this means, i need to set somewhere also manually that users stay logged in forever in XenForo! Hope this make sense, sounds complicated, but it isn't
I don't believe there is an option to force the removal of the timeout feature. You can adjust it (within certain limits), but not remove it. If there is a bridge with amember, then it would probably need to be addressed to the author of that add-on/bridge as not a lot of people are doing this (and it's not built in to boot).