Actually... Regular deep discharges are just about the second worst thing you can do to a LiIon (second to leaving it in the blistering heat, that is. If you also count poking inside them with sharp metal objects, then it's the third worst thing). They stay much happier when topped off before reaching half discharge.

Remember: LiIons are a completely different beastie than NiCads; the latter really craves the deep discharges.