Unfortunately, there is no designated area within the FV to place the stem when not in use, in order to keep the design as compact and as ergonomic as possible. We are, however, working on a stealthy hard case for the FV that will incorporate storage for accessories like stem, brush batteries etc. so you can conveniently take the kit with you where ever you go. Your kit comes with 2 stems, so you always have one as a spare. Furthermore, if you should require additional FV stems, they are available on our website or through any authorized distributors for under $13 for a pack of 5... as always, we keep the accessories priced reasonably so you can always afford to have a few spares around. In regards to the heat build up, yes, the FV's outer shell is machined from 100% aluminum alloy, which has excellent heat transfer properties. The properties of the ceramic core is to act as an insulator to retain the heat generated for vaping inside, while any residual heat is radiated out by the large surface area of the aluminium shell. No additional vents are needed as the entire body of the FV acts like one giant radiator. No sleeve is added to the FV handle because honestly, it is not really needed as it will not get too hot to hold, even with continuous use. This way, you can also get a better physical feel to gauge the temperature of the core (if the unit is warmed up or not), and to better judge how long you should power-on for when vaping. When the unit is completely cold, it may take 5 seconds to get the kind of vapor action you want, but after some heat build up, (when you feel the heat in the handle), it may only take 3-4 seconds to achieve the same thing. We did, however, incorporate 8 channels into the handle for better grip, and improved aesthetics. While there are 3 screens in total in the FV, (the heating element screen, the replaceable top screen that sits above the heating element screen, and the filter screen that you can see through the top window), there is only one that is user replaceable, and that is the screen which your materials comes into contact with while vaping. We are working on making the filter screen replaceable as well soon, by offering a set of custom tools with the screen and o-ring seal available for users to easily replace this filter screen at home. Right now, while it is possible for users to remove and replace this filter screen also themselves, it is a very delicate job, and definitely not recommended after using the FV The filter screen is made from the same grade of surgical stainless steel as the heating element screen and the replaceable top screen, but of a slightly finer mesh variety (smaller holes).