What could be the effects of erosion on a rocky Earth-sized planet on a universal time scale (in the order of $10^{40}$ years)?
Let's assume that:

* The source of sunlight is endless and almost constant, occasionally dipping in intensity causing global cooling. Generally it's sufficient to maintain complex life.
* The planet is in a perfectly closed system, with no external interaction. There are no impacts, and all matter is perfectly confined within an 1.5 radius limit from the planet.
* The polar caps on this planet are always frozen

I'm interested in the consequences at the geological level. Would landmasses still be present after such a long time? Is it possible to maintain some sort of mountains?