Originally Posted by recursive
Mountain bike tires are lower pressure so this makes sense that they don't lose as much. To me, the tradeoff for decreased rolling resistance is well worth the <1 minute of pumping.
If you haven't invested in a good floor pump, now's the time. Topping off tires daily (I have to do it semi-daily, myself) with a frame pump or minipump is for people who just don't like themselves much.