with boots that expensive, only treat with a leather conditioner they endorse that will not void their warranty
for example, lowa (boots I have) void your warranty if you use any boot dressing with solvents that dissolve the glue along the sole, and petroleum containing boot dressing do ruin some boots (environmental concerns means that boot makers now all use subpar glue, which matches with the fact that more boots are having soles come off these days.....this was almost unheard of 10 or more years ago....it just isn't the made in china thing.....maybe this is the tethrd one stick's problem also?)
having said that, i would first treat them using what the maker advocates, be sure to treat every part under the lacings that face towards the foot, etc, etc
next, if that doesn't work, then consider how i fixed a pair of muck neoprene lace ups
you couldn't treat those because they are neoprene
i made a patch out of stealth strips and covered the whole tongue, problem solved instantly