So here is the question. How long computer, without access to any domain controller allow user with domain credentials to log on? I read tons of stuff and now have suggestion that logon is availible infinite count of time, but if connectivity will availible again in more than 30 days it will show the error that trusted relaitonship is lost. Is it true and why?
Without contact to a domain controller, you can logon indefinitely to it - provided your user name is among the last ten (by default) successfull logons that occured with contact to a domain controller. Note that all these ten slots will typically be used up by the standard user logging on ten times in a row. (Alternatively, you can logon to a local account, and of course that can also be done indefinitely).
The trust relationship loss you observe is rather for the machine account logging to the domain, not the user accounts. By default the machine password is changed every 30 days, but even if you do not have contact to the domain for an extended period of time, this should not have effect: The password does not age out at the server,but only at the client (cf. this article) and problems should occur only if something nasty has happened (such as reusing the computer name for a new box or using an old restore point)