Sorry, device charging doesn't work that way. If it did, you'd just hook your mobile device up directly to your car battery and have it charged in minutes.
The device itself determines how fast it gets charged by drawing a certain amount of current. Based on passive or active measures, it might draw more current (say, 2A max) from e.g. a wall charger than from a computer USB port (say 500mA max), but if you decided to just wire two wall chargers together, the device isn't magically going to draw 4A.
As for your Kindle, depending on the model you have (Kindle Paperwhite or Kindle Fire? big difference), it really should charge in just a few hours to the point where it decides it's charged (based on LiPo voltage levels). Sounds to me like the internal battery in your unit may be worn and either the charge controller is dropping charging current way too early, or the battery's voltage level takes too long to reach the 'charged' state during the voltage phase. If it's within its warranty period, try exchanging it.
Of course the other possibility is that your nights are very short