Everything deterioates over time, however im curious as to why so many collectors have such concerns over detoriation and or cracking?. I have even read some posts about death trooper gun holsters that are already brittle or broken from the fuax leather. First things first. You need to understand the types of materials used on these figures, a lot of the Fuax material used for the leather type of materials requires a plasticizer and contains phthalate', most will be (PVC) or similar type material, this allows for easy care and preservation to extend its life significantly, such as using cleaning and protective materials found on various website and they are inexpensive and anyone can apply it so long as its applied properly.
As far as the rubber suits on the troopers and other figures they are made of petroleum-based monomers or (SBR) again this is very easy to keep from cracking or detoriaration, unless you are in a constant cold climate then you cannot avoid the SBR' from becoming brittle and cracking but as mentioned above with the proper cleaning and protectives properly added these materials will last years and years to come even with dynamic posing. it take cleaning and preserving the materials about every 30 days so about 10-12 times a year which isnt much time and effort considering what we spend on these figures.
lastly i recently watched a great video on instagram about people cleaning scractches and markings from diecast figures with application of alchohol, i would never ever apply alchohol to any figure or any type of material not only does it dry out very quickly but also removes the coating used fro shine or other details in the paint. some of these materials becuase they are synthetic and not the more expensive natural counterparts makes them non porous so you have to use cuation, the video showed som egreat tips but also show spraying figures directly and cleaning with a paper towel, i would avoid both, also apply cleaner or protector solution direct to your cloth and always use soft porous cotten or hemmed cotten, microfiber should not be used to apply or use to clean figures only for polishing or wiping surfaces with shine and they should be used dry and lint free... hope this helps... ive done over a year of research on these figures gather lists of materials used in the tailoring and the types of materials used even the types of metals and platics used as well and the paint conpanies they ues to apply their color and laquer etc,, with that said i spent another few months testing how to properly treat, clean and preserve these materials for long lasting figures.
last but not least we should all know very cold temps or very hot temps at a consistant amount of time is always bad and if you are in an area that is either very dry or very high in humidity it is best to get both an air cleaner and dehumidifier for larger more expensive collections, anyone with 50 figures or more should def invest in a Rowenta cleaner and humidifier or dehumidifier depending on location, this will be an investment youll be glad you made.