There are a lot of competing theories of how the universe will end, but pretty much all mainstream cosmology admits that it will end. Very few cosmological models say otherwise.

However, even then I contend that eternity is just another kind of ending. Given an infinite time, everything that can happen will, and therefore it will also repeat. That means that every decision we make will be made again infinitely, every path followed an infinite number of times, always eventually returning back around again, and ultimately the outcome will still be the same.

So you see, under cosmologies of eternity, we just exist in a stasis of infinity and our decisions will not change that. Under cosmologies where the universe ends our decisions will not change that either. Does this mean that nothing we do matters?