semi-frequently. And the odds that it will be fixed in early morning seem low statistically speaking. If it goes down over night, it stays down until they can fix it.
It would be neat if the website (which can correctly identify the server being down) could talk with the server (or itself, if it's hosted on the same machine) and automatically reset things after a crash.
The devs don't do that, because they want to fix the problems that lead to the crash first, before they restart it. Otherwise the server could crash every five minutes, data could be lost, bugfixing would be more difficult, and nobody is helped.