Yea lithium ion batteries and chargers are both built to not overcharge, after it reaches 70% charge it cuts the power in about half and keeps decreasing power to it as it gets more and more full, in fact your battery will never actually become fully charged, even though it will say it is.. this is a safety feature, even one milliamp over it's rating will make the lithium unstable and seriously dangerous.. so.. it's ok to leave it on it's charger as much or as often as you want, it's built to keep anything bad from happening..
..same with overheating in the case, it won't.. if it starts getting hot it will decrease the allowed voltage into the cell, this is built into a chip in the cell