The bad news is these rockers usually rust from the inside out, so by the time you see some rust the damage is extensive.
You sir are correct. The key is to keeping the paint/metal clean. Some of us that live in the frozen tundra 6 months a year (aka they salt the roads) have a little harder time keeping it clean.
The tape on the back side of the rocker panels was placed there so you can access the back side of the rocker panel (where it rots from the inside out). A body shop that I talked to stated this to keep the rocker from rusting:
Remove the tape from the back side of the rocker panel (lay on a creeper)
Stick a hose in EACH hole
Wait for the water to come out the bottom drains as shown in one of the pictures on here. You will likely get soaked so save it for a warm day...)
If water does not come out the drains, they are clogged with dirt/debris and should be unclogged. (You can use a little mirror on a stick and see in there easily)
Once you see CLEAN water come out of ALL of the drain holes, let it dry completely. I sped up the process by using my girlfriends hair dryer.
Then clean the back side of the rocker so NEW gorilla tape (or similar) can be applied over the holes. I also used the hair dryer to warm the metal around the holes because it was 45 degrees outside when I did it last. This tape will keep any more dirt/debris, that could plug the drains, out.
I was told to do this ONCE PER YEAR, but tape and hose water are cheap, so I will likely take a look at the condition of the tape and address it as need be. My 2001 Supercrew was victim to rotting rocker panels and I am determined to not let that happen to my 2013.
I will add pictures of mine when I get a moment.