Hi,
Im no expert with autoboxs box there might be slightly more waer on the clutches because of more slip with the box,but TBH i wouldnt worry about it to much if you find the car easier/nicer to drive in the wet.On other car i used to own i did the same thing,driving in snow mode in the wet.There was no traction control on that one and i found i had better traction when pulling out of a junction what with moving and turning the car.The car also didnt have a limited slip diff.
Chips.