as stated above, use them occasionally every month, turn them on, shift them in , drive for a bit..shift them out, shift them in , shift them out.
For me this time of year its kind of the opposite. Since I have to be in 4wd every day. At least one time every 2 weeks I will take it out of 4wd and drive it shortly, shift in , shift out, shift back in and leave it in.
With my elocker, if I have not used it in a week or two, I will shift it on go a few yards, shift off, shift back on and run for a few miles, up the hill to home, then off in time to make sure it disengages before parking.
mind you , in both cases, im in the snow and ice all day and rarely see black pavement.
summer, when bare roads...all are in 2wd, but I will run the 4wd every few weeks, or use the 4wd when pulling a boat out of the water ( rare only if taco or ford are not avail) or climbing steep or rough gravel roads ( which is every few weeks at least)
and of course, stay on top of fresh fluids, greasing ujoints and constant inspections