If the weather's poor , road conditions are crap , or if you are going off road, lock the hubs BEFOREHAND and shift into 4hi as needed. If the weather is clear keep them unlocked. Lock them in once a month but do NOT shift into 4WD, just run a few miles, it will keep the front end seals from drying and the mechanism from freezing up. I would MUCH rather have manual hubs then the damn auto ones. Fords were especially poor, and I would immediately put on Warn lockouts as soon as I bought one. [You also do NOT want to know what auto hub replacements cost, as Ford obviously thought they were made out of solid gold, and not the pot metal POS they actually were made of.
Just do not run with 4WD locked in on dry roads or you will cause bind in the drive system and possibly end up with a $$$$$$$$$$ bill.
Where are you at in MI?