As the server host guy I wanted to know if you had some ideas to stop a server from dying by changing the servers goal and not by modding the server ( Create Mod, ... ).
I'm gonna be honest, if the players are getting bored so quickly it's mostly their fault. It means that they aren't ready and/or capable of going outside their comfort zone to construct i.e. a megabase or giant farms etc., maybe because of the fear of getting grieved. If these problems happen frequently, than the players are probably just not the right persons.
But I can relate to your problem, and know how hard it is to get the right people to the right place