Well first of all, this isn't really a suitable section for this topic. Help is meant for posting about problems with blockland, not advice on how to run your server. Anyways, as for the administration problem, just get a few admins to help you moderate while you're afk or even gone, if the server's dedicated.
As for the problem of players getting bored, this is complex issue. You can't simply host arctic survival RPs anymore now that slopes is gone. Disabling player building is only going to make things worse. Unless you've built an actual map with decent terrain, it's no wonder players are leaving and getting bored, with just a few tents slapped on an endless slate. You need a decent terrain map which is very large and has plenty of stuff for people to do. People like to contribute to the RP too, meaning they like to set up their own tents and such, which is where administrators come into play to watch for spam.
Hope this helps!
