I've always put my phone on a charger every night regardless of battery level going back to HTC tilt and have only had 2 devices junk a battery same goes for my year old moto 360, battery life has been the same for 7 months now. Do batteries go bad? Absolutely, is there a cycle life yes but it's a very wide range with a lot of variables. I wouldn't stress over it.
One of my big hobbies is RC car racing and we use lipo batteries, not much different then ion, they have a cycle life as well and supposedly no memory (sorry but both do have memories) One of my packs is almost 3 years old and is one of my best packs where I just had to throw a month old one out, same brand and manufacturer.