This really depends on individual physiology.... Not something that is the same for everyone. It is also something that happens to all of us .. newbies and e-cig veterans. It really deals with oversensitivity with the taste buds and proper hydration. Most of the time when I get it ... I usually switch out flavors to something that is a dull flavor or even flavorless .. just for a while to help alleviate or give my buds a break. If you normally use a device that gives you a lot of heat value to your vape... You may want to switch out to a cool vapor set-up, as well.. heat has a lot to do with cotton mouth and can affect vapor tongue, as well. I have a cheapo MOD set-up with a LR atomizer that I found vapes at a pretty cool temp with a clearo and I always just leave that set-up with a lite flavor juice that is not too harsh on the buds.
I am a heavy vaper .. So, I can leave all my normal use mods set-up for my fave Heat and desired vapor output... But when the tongue hits its final notes... I can switch over real quick and jump back a little sooner than later..
Depends on the equipment you use as far as cooler vapor delivery..... If you are using a standard battery set-up.... avoid LR atties because they change the resistance through the coil which delivers more heat to your vape. Best method to take this a little further, Get a tank system with a bottom coil set-up ( evod, Kanger Pro-tank, ex. etc) and this will allow for cooler vape due to more air travel before the vapor reaches the mouth. This is also why a lot of folks on ECF have been saying that the bottom coil tanks seem to be a real "airy" draw.
If you are
vaping using a VV or VW MOD... remember lower resistance coils with higher voltage / wattage = equals hot draws. I always try to balance and equalize this during tired tongue by veering from my usual.... 0.8 to 1.8 ohm coil @ 4.4 to 5.2 volts is my usual zone and I am a very heavy vaper..... say 4 to 5 tank fills a day ( roughly 10 mls +). I also vape quite a bit with 0 nic so don't be too alarmed.
Just try to back off for a while evry now and then should the tongue start complaining about overtime. Say.. 2.2-2.4 coil @ 4 -4.4 volts.
Hope this helps

TOM
P.S. - As always, try your best to stay hydrated by drinking plenty of water while you are vaping. desensitizing your tastebuds by eating different fruits and brush your tongue really good when you brush your teeth has been known to help with this as well.