Yeah, what about a lifetime warranty, does that seriously mean I can return it anytime..
I not 100% sure about this as I have not read into it in detail, but most companies will replace the RAM as long as you have it and is determined to be factory defective and not damaged by any type of missuse. I dont know if they will replace RAM that was damaged by OC past the factory specs. I would assume no. It must be defective though you cannot just return it on a whim. Also I belive most other brands of RAM offer the same thing.
Here is a link to the details on Mushkin Warranty