I haven't noticed the resistance changing much. Over a long time it would tend to increase slightly since more of the coil material is oxidized and won't conduct as much current, but I don't think that's the major failure mode.
I think the major thing that causes atomizers to slowly degrade is that the coil and wick become encrusted with the stuff from your ejuice that doesn't completely vaporize. The wick doesn't draw as much liquid up to the coil and the coil is now insulated by the crust and doesn't get as hot at its surface and won't vaporize as well. You will notice this happening quicker with dark colored juices and VG based ones.
Maybe you could use two attys in rotation, take the used one, blow it out and soak it overnight in alcohol, rinse it the next morning and let it dry during the day while you use the other atty. That should minimize the buildup inside the atty but it's a lot of trouble to go to, adding in the necessity of priming the cleaned atty each morning. It does have the advantage of eliminating stale overcooked juice, so the atty should taste fresher.
For myself, it's mostly cartomizers now. With a variable volt PV and the better quality cartos you can get good everyday flavor and vapor production and skip most of the hassle. I just use attys for testing new juices and switching between several flavors when vaping at home.
