Like some that do or like some that don't...it's basically a personal choice. Moisture is the biggest concern. Years ago there were some collector plugs that were sold through Dan Dvorak, made of stainless and filled with desiccant that would draw the moisture out of the engine on the exhaust side. Memory (?). hmm... he stated to drain/remove the carb and silicone the areas that needed sealing in an attempt to keep all moisture to a bare minimum, he may have even mentioned backing off the valvetrain as well. From what I recall, the pair of plugs were about $125/set, at which point, I bought a set and they work quite well too! Nonetheless, good engine off-season storage/maintenance has been pretty-well covered in the above posts...eliminate the moisture and you're good, don't eliminate it and you'll have short-life in your expensive race toy!