None of the manufacturers of any of the Li-ion batteries I own, in several cameras, phones, and other gadgets, has expressed any preference for charging frequently after each use, or less often and nearto battery cutoff point. I therefore presume it doesn't matter much, provided you use an appropriate (usually dedicated) charger, so that the charging software and protection and that built in to the battery can interact properly.
HoweverI'd expect running it low and then leaving it for very long wouldn't be a good idea, in case it became very low in charge during lack of use. I returned to my Li-ion powered, seldom-used pocket camera yesterday, after very little use in the last year, and found it still turned on and worked, but it showed 'battery low'. My camcorder uses its battery power quite rapidly when not in use, presumably because it's wasteful in its clock and settings maintenance.
If you top up the battery after every serious use, obviously it lessens the danger of allowing the camera to flatten a partly-discharged battery completely while not in use.
If there are any proper battery experts lurking here, it would be nice to hear their opinions. Otherwise we have only Wikipedia and the wonderful http://www.batteryuniversity.com
, and Isidor Buchmann's other publications to go on.
Remember that Li-ion batteries have a limited lifetime compared to other types, whether you use them or not. For longevity, it's best to store them half-charged, in a refrigerator, according to Prof.Buchmann and others.