This stress will eventually lead to failure of the rubber at it's weakest point.
That's why any of the HT Alien jaw tendons will eventually break because the mouth is left open. And why your Kane's knee will break because you keep it bent.
Uhmm, my cars door rubbers are 10 years old and haven't cracked. And they open and close everyday, 5c rain, sleet, sun, 55c summer winds, they're still fine.
Think about it it's a business model that HT uses.
a.) Make the products out of lasting rubber compounds that are slightly more expensive to produce? Your production costs go up. Add to that the fact that returns on products will be low as all figures will meet the expectations of clients.
b.) Make them out of the cheapest air forced rubber compounds for vastly reduced production costs. Knowing that your target market are collectors who at the first sign of wear will replace their purchase with a brand new one and you'll get incredible revenue.
It amazes me that some people think that the management of large multinational companies and distributors are a bunch of highly educated, serene, balanced well intending group of helpful people.
In reality (as you can see) the management at Hot Toys are a group of get rich quick low life cowboys intent on S_H_A_F_T_I_N_G their target customer base for every penny that it's worth and enjoying boosting their golf holidays and poker funds.
and ye sheep willfully and joyfully bend right over.
In the mean time use rubber sealant every few months(available from any high end automotive detailer) on the figure's rubber. This will replace the natural rubber moisturiser in the compound (it's the depletion of this that causes cracking).
You might want to test a few products for shine first, see what you like. Smartwax and poorboys sealant leave a satin finish when you buff them out.