If it is largely due to grit, then gently removing it should cut the risk.
Still puzzled why cracking seems so rare in things like gloves, some of which live fairly hard lives.
DW, from your experience with working cowboy boots, did you see a difference in longevity based on how carefully a client maintained his footwear?
Of course, but the thing that makes the most difference...in my opinion...is keeping them clean.
That, and keeping them clean.