I ran a set of the Airlift1000 extended bags with zero air pressure and the valve stems removed for over 2 years, granted was only about 10k miles total.
I had no problem with running them on zero air pressure, when i pulled them out i cut the bags open to look at wear. Did not apear to be any damage from no air... got the idea from another member on here... was thinking it was working as a sort of air jounce/bump stop.
Fast compression= less air can escape.
Slow compression= more air can escape for better articulation.
This is all theory and conjecture on my part of course.
They work great for added weight and towing too.
I have use them the proper way as suggested for years before and was happy.
Eibach makes a rear adjustable coil for the 5th gens, dont know if its a 4th gen compatible, but i dont see why not.
Load leveling kit.
Eibach 5th Gen Rear Load-Leveling Kits