As much as possible leave them uncoiled. G1 wise - the cassetticons - Rumble Frenzy are a good example of springs losing their "springiness" ( for a lack of word at the moment) easily. You will mostly end up with a head leaning to one side or the other. But with 20+ yrs old toys you cant really expect it to last forever, however for newer versions, Id say leave the missles off and store em separately (and prevent loss) as it doesn't lose much anyway in aesthetics while displaying/playing them. Some toys though are just freakin hard to get the spring to ease up - Unicron chest spring comes to mind - of which I completely disabled the feature in my toy otherwise I end up with "burst open unicron" due to the strength of the clip not equal to the strength of the spring recoil on this particular toy... hope this helps