I use these with a set of Harman/Kardon SOHO II NC Active Noise-Cancelling In-Ear Headphones.
These are far more comfortable than the supplied ear tips (particualry the plastic ones) keeping my ears cooler for longer. They also provide increased sound isolation and can therefore monitor at lower volume levels.
Generally they last several months depending on usage.
Only negative is that they do seem a little expensive but they are a quality product.
Overall highly recommended.