Here's a page on battery university, a highly respected site that's built a good reputation for many years, about the care and feeding of lithium ion batteries.
http://batteryuniversity.com/learn/a...ased_batteries
I haven't read the article in a couple of years but basically, as I recall, assuming it hasn't changed, it does say devices batteries will last longer if you charge them sooner. There are a number of tables and charges on the site showing that.
However, the difference is small. You'll improve the overall lifetime of your battery by smaller shorter charges done more often but not by a lot. Personally I'll take all I can get so I charge all of my Kindles every Saturday and I charge the one I'm currently reading on when the gauge get's noticeably below full.
I've been doing this for years, carefully, and my Kindle batteries are all good.
However, all of my older Kindles are in the hands of my neighbors, many for several years, and none of them give the kind of care to them that I do. Quite a few let them go dead before they think of charging them. And all of their Kindle batteries are holding up just fine.
So there probably isn't a lot of point in worrying about it unless it just makes you feel good, as it does me.
Barry