Just stay hydrated and switch flavors more frequently.....it's the one flavor overload that causes it, and it's not your tongue it's the scent receptors in the back of your throat that are overloaded....
Big Picture Science
I concur with the above statement... With two additions!!
If you are drawn to vaping mostly very strong overpowering flavors... Get used to having vapers tongue!! It is best to regulate yourself a little and pace yourself. Keep some muted flavors around to switch off to when the tongue monkey comes around. Vape those for a few hours or so to help subside and give those receptors a break. Another good thing is to keep some mild losenges like say ludens or ceprocol to help sooth the back off your throat from time to time.... Not all the time, just when your notice a little discomfort coming on and especially after you have an all out vapefest.
Secondly, another big part of this comes about from irritation to the salivary glands throughout the mouth. This is not only caused by the oversensitivity to the taste buds and olfactory(smell) senses but, Nicotine in high concentrations per ml ( 22 and above) will cause irritation to the tissues of the mouth because that is where it is making contact in its highest concentrations for absorbtion. Case in point, a lot of snuff and chew users encounter bouts where the tissues of the mouth in the areas they pouch the tobacco sluff or sheed the surface tissue and become sore ( hence , most folks that use these products constantly change the position in the mouth that they hold their chew/snuff ). The best thing to do here is ... If you are above 22mg/ml then, get some juice that is at least half the mg and trade off on a frequent basis to prevent excessive irritation. Would not hurt to taper yourself down to at least 18 mg and most of your problems with constant recurring vaper tongue will be addressed outside of the occasional overload on the senses with strong flavors. I only state 18 (although it may be a little different for everyone) because that is where I found I didn't get vapor tongue on the continual basis and I used to get it several times a week... Now I can usually go for months and then, maybe during a vaping binge I find myself back in the boat for an episode.
Hope this helps!!

TOM