Offline Growth

A lot of people have quit playing Minecraft. And with a simple task of playing regularly. You could keep cobwebs and vines from growing inside your base. This would make people want to get on so they don't have to come back to a messed up base. Over time even cracks could form in bricks or walls of you base.

This could even be a gamerule so you don't have to worry about your base decaying on a really cool world/creative world