Had the same issue initially. I'm fairly sure that 1-2h charge will top it up from a wall socket. Haven't plugged it into my PC to actually check the charge but that's been what I've read and it's yet to die on me from use. Given my experience with similar devices, just make sure you charge it for a reasonable amount of time before any extended use and try to avoid charging it after use unless you're sure the battery is dead. Unless something is fucked on the hardware end, that will probably hold for most applications. None of the components (that I'm aware of) should cause a huge battery drain like a screen or wifi would. So you can expect the battery to hold for quite a while. I've also read (but cannot confirm) that the hardware will prevent overcharging of the battery automatically. Still wouldn't leave it plugged in when not required - but that's just a sane battery health precaution.
Do wish the LED were a liitle more indicative of a full charge. But, to be honest, that's a fairly minor issue. When in doubt, charge it a moment more. Unless the battery is actively dying on you despite charging before use, I wouldn't worry about charge too much.