It is amazing how Phdcomics reflects my life in Grad school. I used to tell my advisor exactly the same thing, only to find that I had "no time" nor inclination to get anything research-related done while back in Singapore. I've stopped "lying" whenever I take my trip home nowadays (and my advisor knows better than to expect any work from people going home anyways). The way I cut down on the lack of productivity is to avoid going home for more than 2-3 weeks if I can avoid it.
Ok, this will be my last piece of procastination for the day :P.