One persons waste is another persons... energy?

This week in class we learned about how the methane gas released from wastes in landfills can be converted to energy and put into the grid. I thought this concept was extremely interesting and a good idea. I looked on the EPA website and found that there are over 445 landfill gas energy projects (lgep) that are already operational across the US with over 500 potential projects in the works. The EPA estimates that the lgeps generate about 11 billion kilowatt-hours of electricity per year. The fact that there are many projects in the works is evidence that they operational ones are working effectively. I believe that these projects are a good way for us to move away from fossil fuels for creating energy. One thing I was curious about in relation to these projects is to what happens once the landfills stop producing methane gas? Would the equipment be able to be moved to another landfill and used or would it become waste itself? I am also curious as to how much maintenence is required for lgeps. Despite these questions I really like the idea of using our waste in a beneficial way.