Well it would certainly be fine to charge it up a certain amount and then "finish" the charge, although not all
batteries retain "memory" although to be honest, I'm not quite sure how that works, because I have charged up batteries that weren't fully discharged, yet my (external) charger showed them at partial charge. It is good practice to remove batteries when fully charged, although my understanding (which I will admit is hazy) is that most charges shut off and don't draw more current unless they are attached to the device for so long that they require "retopping" I mean, I don't worry about leaving my cell phone to charge overnight, and I've never had any problems.
I think you can still HAVE problems though, and if you feel safer watching it while charging or at least keeping an eye on it, well, that would be good practice. I don't leave lithium ion batteries on my (external) charger overnight if I can help it, so I'd definitely agree that it is the safest battery practice, as you just never know when something might go wrong. So I would say, go with your instincts, if you can make it work for you. It shouldn't harm your battery or device, although it may (potentially? possibly?) cause the device to need to charge a little longer, as each time you plug in a charger, it may start charging at slightly below whatever your charge was? That is what I have found with some of my internal battery mods, but I don't think that it stresses the battery unnecessarily.... And if that is what works for your safety and routine, I say go with that.
And I apologize upfront, I am not a battery "expert" I am going by what I have seen when charging externally and internally and haven't had any problems with my "no charging overnight" strategy. I actually leave my charger in the bedroom just in case I ever forget.... But far away from whomever wakes up first (most likely my husband, I can sleep through Armageddon) in order to deal with it.
Folks will often isolate charges (USB or otherwise) by placing the device (mod in entirety and/or battery charger) in a heat safe enclosure to minimize any damage that could happen by charging, e.g. it's easier to take an overheated or venting battery outside when in a baking safe container or something.... But these are rare incidents, for the most part.
Anna