There are limitations to any and all parts on your vehicle, custom aftermarket and factory. Knowing these limitations can keep your parts and overall custom vehicles health top notch! To get to know how a custom air strut works you need to know how a shock works as a strut is simply a shock with a means to support the vehicle attached (coil spring) making it a complete assembly. Below you will find a picture of said strut assembly to get an idea of how this part works.
If you take a look at the illustration above you will see the issue with over inflating/extending and under inflating/collapsing a custom air strut assembly. The main issue lies within the internal structure of the shock portion of the strut assembly. Excessively pushing a strut in either direction while the vehicle is at rest is fine, though while driving this situation can cause serious damage to the internal seals and piston within the assembly that is normally not visible. As you can see from the diagram above, if the strut mounted air bag is extended to the max and then the weight of the vehicle traveling hits inconsistencies on the road a hammering effect in the upper portions of the strut can bee seen. The strut/shock piston will slam against the upper strut body cap and can possibly create metal debris and other damage to occur within this sealed area hindering your inoperable and putting a major amount of excessive wear on internal components. It is essential with air struts to keep them approximately 1-2 inches below max, and 1-2 inches above collapsed while driving to avoid any of this damage from occurring with your new air ride hardware. This situation does not apply to air springs with no shock attached or standalone air bags with separate shocks.