R&D plans and R&D parts needed to assemble gear are bound to episode cycles, e.g episode 18, 19 and 20, and will only produce gear dropping from those specific episodes. Every episode cycle will have items which do not drop from playing content and thus exclusively are available as R&D Gear. Introduced with game update 54 R&D Gear is primarily meant as a last resort to obtain gear not dropping as loot from doing content. It is not meant to replace the need to play content to get gear, thus its assembly costs and parts gathering time have been made quite expensive.