Your experience with the istick sounds like bad luck. A brother of mine has vaped an istick 20 exclusively for the past 18 months. I can think of no rational reason why resting them would matter.
I'm thinking a lot about durability these days because of the FDA. My favorite form factor is the Pico. The USB port needs to be treated gently. The part that takes the most wear is the fire button mechanism. I press the button 5-700 times a day. That adds up. My solution, get 5 of them before August 8 then get 5 more of something else in case there are shelf life or other issues with one or the other. With all that I'm not expecting more than 10 years from all 10 but may be they will do better than that.
I plan on getting a few more too, but I thought come August 8th, anything on the market up to that point could continue to be sold for 2 years while paperwork and so forth is dealt with. Am I wrong? If I'm right, what is going to suck, is seeing everything else that gets released elsewhere in the world.
As for wear and tear, I've been using mine non stop as my only device since March with no issues for what it's worth.