It doesn't matter how it looks. It's the thermal properties that are reduced over time. You are welcome to go to the AMD website to read a more detailed explanation. Arctic Silver 3 was intended for people who remove heatsinks and/or processors often, such as hobbiests or developers. AMD recommends using a thermal pad for long term installations, which I think is crap. With Arctic 5 the properties are more stable and do not break down with time. I know that with my setup, the processor temps do go up over time, not much, 1 or 2 degrees only, using Arctic 3. Don't know how Arctic 5 will behave over time, but so far, I like it better than 3. It's suppose to be a different formulation than 3. It is thicker and darker in color. I guess only time will tell if it is better.