Li-ion Batteries, care and maintenance

I have a number of batteries including Li-ion batteries for my Sony F717. The Sony batteries have been in continuous use since the summer of 2003 so their lifespan isn’t quite what it used to be. This page suggests that Li-ion batteries, “should be continually topped up! Unlike NiCads you should not let Li-ions run flat as this will effect the life of the battery. Always top them up whenever possible.”
I’m charging mine now just in case!