How Long Does the facebook maintenance usually last?

When ever I try to log into Facebook, it says my account is under maintenance, i was wondering how long it usually lasts.|||Yes a maybe a few hours . i didnt even know that and asked a question about it lol|||I have been on facebook three or four times tonight and it's working fine for me. I am in the south eastern USA. North Ga|||Depends, normally a few hours though|||a few hrs atmost